Ive been playing the guitar since i was little, now im 14, and a few years ago i fell off a bike and hurt my left arm, i never got a diagnosis and assumed it was a mild sprain that would soon heal. but lately, i cant even play an entire song on my guitar without extreme discomfort and for the past 6 or 7 months, i feel a long, narrow… something, popping all the way down my arm, when i move it. after use of the arm, it pops like that a lot, and then hurts for a while. sometimes the pain moves into my hhand and next to my thumb as well, but the popping is on the side of my arm and sometimes its particulary loud, loud enough for others to hear. it sounds like cracking your knuckles but in the side of my arm [NOT wrist]. what might this be, and what can i do about it?