I have a bump on the bone of my shoulder near the AC joint but no bruising, it is pretty painful but only hurts bad at certain angles. There are some angles that do not hurt much at all. It is not my muscle or ligaments but a bump on the bone itself. I received this injury during MMA practice and may have taken a blow to the shoulder, however I do not remember this happening, in fact it did not start to bother me until an hour or so after practice.