my 12 year old son was playing baseball a couple of months ago and heard a pop in his shoulder followed by pain. xrays and an ultrasound came back normal, our family doctor said it was probably soft muscle damage and would heal in 4-6 weeks. it has now been 8 weeks and his shoulder is still very sore, and his hand goes numb at times. he is a goalie for hockey and is worried he won't be able to play again. what could this be?