Body aching the next day after weightlifting

if it's a general ache that hurts more when you move around, and also you may feel a bit stiff... that's normal. Don't decrease your reps or anything because of this. Just make sure you're getting adequate rest between workouts (each muscle group/body part should get a day's rest at least, so if you do legs on monday, you don't do legs on tuesday but you can do legs again on wednesday.... if you're doing a whole body workout then don't do it on two consecutive days. this wont' reduce the amount of achiness, but it's important in order to give your muscles adequate time to recover.

If it's a sharp pain or if you're in enough pain to stop you being able to walk and do normal things, that's an injury and should be treated

note: being unable to sit on the toilet easily after leg day isn't an injury... in normal recovery there's a degree to which doing stuff hurts and you have to do some things more carefully... but if (for example) you can't put your weight on your leg because your knee hurts then that's an injury. Or if you pull a muscle (as opposed to normal soreness) then it is a sharp pain that limits the amount you can use that muscle.

You're too young to be overly sore. If you're putting maximum effort into every workout and doing every set to failure or beyond, you're probably overdoing it. It's easy to let your enthusiasm get the best of you when you're just starting out. The body has to be trained to get stronger and workouts need to be cycled for optimal results. I recommend Jim Stoppani's Encyclopedia of Strength for additional guidance on workouts.

You may also be short on rest and food. I consume a gram of protein per pound of lean bodyweight on rest days and a little more protein on workout days. The extra protein helps with recovery.

Is the pain in your muscle bellies or in the joints/tendons? The first is good and you will notice it less over time, the second not so much. Be careful when you exercise with weights to use proper form. If you don't know what the proper form for the exercises you're doing are then I would recommend checking it on youtube. That can certainly help to prevent joint and tendon injuries from repeatedly occurring. The muscular ache will start to lessen as your body adapts to training. I just get a dull ache the day after training which soon passes now but is a sign that my workout was effective.

I used to hurt terribly when I first started lifting. Now I'm just a little stiff and sore the next day.
Lets me know I did a good job.

I used to feel that way the day after Stronglifts once the weight got heavy....well heavy for me. I finally hit a point where I was no longer feeling that the day after. Just everyday. Eventually I got to the point that even though I was hitting my limits and having to deload regularly and I wasn't feeling anything. I didn't like that so I swapped up to higher rep sets to get that feeling back. Okay maybe a little masochistic but it makes me happier. However, if it is specific to muscle or location there may be a muscular or skeletal imbalance.

I mention it only because it is something I have had to deal with. That kind of pain isn't the typical soreness that drains away over time. It was constant sharp pain whenever I moved those locations. It was specific to my right shoulder and the adductor brevis in my left thigh. After having repeated pain in the same areas over and over that never seemed to fade I spoke with my doctor about my concern. We had some x-rays taken and found that it was due to a slight twist in my hips when standing. Basically a mild case of scoliosis. My left hip naturally twists forward when standing. As a result I would end up putting more downward pressure on it making it want to turn inward at the hip even when pressing my knees outward. To compensate for the motion on the left my right side was rising first. Thus the right shoulder taking the weight when pressing or lifting up. It was causing severe pain with squats and deadlifts. Once I understood this I was more mindful of centering my stance and letting my left be slightly further back than my right. Making especially sure my stance is open enough. Since this is a twist forward and not a height issue a shoe lift is not a fix as I have often been asked.

I am not suggesting to you or anyone that you or anyone else has an imbalance. You did not mention anything about a specific pain you just mentioned body aches. However, if you or anyone has pain when lifting be mindful of it. Check your form. Do a mental checklist and engage the muscles before the lift. Give yourself warmup reps to make sure you aren't feeling 'off' before you lift heavier weight. Lifting has made the best changes in my life and has also made me more aware of myself. I suggest it to everyone. Soreness is typical and to me a required aspect.

This is what I do:

Monday - Arms, shoulders chest

Wednesday - Back and abs

Friday - Legs

Switch to a full-body workout done every 2-3 days. Problem solved.