Here's my experience with what you are feeling. A few years back, I had the same type of pain and ignored it. I was working chest/triceps one day and some dudes jumped on my station before my last set of lifts. I decided to stay warm and do some light preacher curls using some light, 25lb dumb-bells. Did a set of 30 with right arm and on my 5th down with my left, my bicep tendon ruptured, completely tearing from the bone. Had surgery to reattach and doc fckd up the surgery, severing my radial nerve, with the tendon rupturing again 4 days later while in a full arm cast. I've also recently had/have the pain in my right bicep and have found through an MRI that it is from a pinched nerve in my neck. I also have some tingling/burning in my left outside fingers while in certain resting positions. My suggestion...have a good doctor that specializes in sports medicine check you out. The doc will most likely order up an MRI and make recommendations from there.