First off, I'm no doctor. I don't know anything except what I've experienced. If pain persists I'd see a doc.

However, I tend to overdo myself a lot. I have a perverse pleasure in repetitive type sportsand a tendency to develop tendinitis.
I've had it all over (never in my upper arm), but elbows, wrists, hamstrings, knees. Sounds like you have a mild case of it to me.
Ice and an anti-inflammatory are the key. You might want to back off a bit of whatever is hurting it. I have trouble with hamstrings a lot because of cycling, and I don't feel it when I'm riding. However, afterward the pain hits and out comes the ice and ibuprofen.

On top of the exercises AP mentioned above add some stretches in there. Do it daily and don't overdo it at first and it helps keeps everything loosened up a bit.