It's hard to describe this but attached my sternum are boney lumps. Tehy dont move or anything, there just set in the bone. It is noticable, and also kinda ofsets the right side of my ribcage. I think due to this, my left side kinda sinks also. Also, on my forehead, right side, is a slightly raised mound of bone, not as noticeable though.
Bone bumps on chest
I don't understand how bony bumps on your sternum would cause your left side to droop. It sounds more like scoliosis (lateral curvature of the spine) to me.
It could be scoliosis. I have a case of it, and I always wondered why i had bones like that as well. It feel akward, doesnt move or anything..but you know its there.