Truth be known, I don't quite remeber, between being "jacked up" for my lift, and being piseed at the other guy for pulling my arm out of place, i can't really recall when the pain started.
I just know after i woke up the next day, I felt like my arm was going to fall off.
I wouldn't be suprised if it happened when you jerked it back for the third rep. I hurt my lower back during squats. No it wasn't during of the the reps, i paused up top and did a little shuffle trying to adjust the weight, when i went for the rep, i felt an odd pinch, finished the rep and felt hte pain the next morning.