Re: bump on sternum
well, as you might know, the ribs are connected to the sternum via apiece of cartilage.
i guess your cartilage, through an unknown process, could have become impacted, broken, displaced, or has grown and abnormality.
if you follow the logical line of the affected rib, does it move freely? do you have pain from pressing on it?
theres alot of things that could have caused that..