A friend of my has one of those bumps...he says it keeps his shoulder bag from sliding off!
I crashed a couple of Julys ago and acquired one of those bumps. After studying the X-rays and not finding any broken bones, I figured out a PT program for the shoulder. I found out that if I grabbed a door knob and over rotated my arm at the shoulder, the bump would diminish. After a year it is gone. Still "CLICKS" once in awhile.