My husband was doing a push-up at his correction class and came down hard on his knuckle to his chest. His chest has been hurting him badly for a few weeks now to breath deeply, cough, or sneeZe and now has a bump where he hit it... What could this be?
Hi and welcome to Chat Doctor, This is due to injury only.  There may be some stasis of blood.  Take x-ray of chest AP view to rule out any fracture of rib.  Apply Tomophobe locally.  Wish you speedy recovery, Thanks