Let me make a guess, it's the area near the elbow and triceps that is causing the pain. Mine is incredibly tight and tender and I lift weights too. (I'm right handed so it's my right arm that's tighter) I take a lacrosse ball or could use a foamroller and roll the area to knead the tightness away. For some reason, that area gets tight which will cause some shoulder immobility if it doesn't get treated.

I've been doing pullups recently with assistance on the gravitron machine. I am fine for 90% of the movement but my elbow starts to hurt at the bottom of the pullup - right before my arms return to the straight position. Has anyone experienced this? Any thoughts on what it can be? It only hurts at that particular point and never afterwards. I wind up having to stop for a second and then I can go straight back to the full hanging position before completing another pullup. (FWIW, I have been lifting for years and am strong and in pretty good shape. I used to be able to complete a full set of unassisted pullups but haven't been doing them for the past two years so I am building back up.)