I have the same thing on my elbow, I was wrestling with my friend and i got dropped on my elbow on concrete. It chipped it, and it swelled and filled with fluid. I dont know if its the same but when I move my finger around it it makes cracking noises. So yeah I suppose if yours is like mine its just chipped.
"They say the only way to kill a lion is with a rear naked choke, but I'd just kick it in the head"