Patient: "Doc, my arm hurts when I do this!"
Doctor: "Don't do that ..."
Probably it's just some mild RSI, and you RICE it -- Rest, Ice, compression, Elevation. NSAID for pain and all, but pain serves a function, which is to tell you something is injured. Better ease off, and if it doesn't get better, get it checked by a qualified medic. Diagnosis and treatment over the internet can be iffy ...
Steve