Hip Flexor Strain

Apparently, I didn't stretch properly before starting a new walking program and strained my hip flexor - I'm not in severe pain - just mild pain when getting up and down from a sitting, lying position, getting in and out of car, mostly. I keep thinking if I just take it easy, that it will work itself out. I've made the mistake of trying to garden, etc. But - it seems that even something mild like vacuuming/cleaning for a long period of time takes me back to square one. I've been reading online and it looks like there is basically NO cardio I can do in the meantime that will not damage it further. Despite that I've tried some leisurely type walks, but that also makes it sore. I've been doing some "glute" exercises to strengthen the opposite muscle. (Interestingly, the first night I did these, I re-strained it (again), so I'm trying to stick to exercises that I know won't hurt it more.)

I'm getting extremely frustrated because it seems that all I can do is sit in a chair and do nothing until this goes away. That's not very realistic when I'm working, taking care of a home with two big doggies, etc..

Because I'm not in severe pain, I don't think a doctor's visit is justified for now. Anyone know how long it takes something like this to go away? I'm definitely no athlete, but I hadn't realized how much better I feel (all over) even when I just do the cardio machines a few times a week, so I'm ready to get back in the game. I know the exercise doesn't significantly help with my weight loss, but it has a hand in it. (I've decreased my daily calories a little to try to compensate)

These community boards are so active with great advice, that I thought this would be a good place to ask. All tips and advice are GREATLY appreciated!!

Lesson definitely learned about stretching before ANY kind of exercise.