My 16 year old son has a lump on the top of his right shoulder. He does not recall injuring it. Painful only slightly when he moves. More sore than pain. Between the size of a marble and a ping pong ball. Maybe about the size of the old super balls. Discomfort when his backpack strap rests on it which is frequent but he does use both straps simultaneously all time time.
Hello, Thanks for using Chat Doctor.improbable diagnosis