whats wrong with my shoulder? it hurts

samco66

i tried to workout yesterday but it was a complete fail. first i tried to run but every time i took a breath in through my nose my forehead burdened really bad which was causing a horrible headache, it was like i was breathing in -20 degrees air. So i tried to do my arms, the second i tried the machine where you pull the bar down toward you it felt like my muscle was popping out. It was the muscle that is on the top, back of my left shoulder right below my ear ( close to my neck). it feels like there's a knot on my shoulder/ lower neck area and its popping out every time i pull the bar down and it hurts. . what is going on with my shoulder? i really want to get back at working out but if theres somthing wrong i should fix it first before i lift.