When I Raise My Right Arm I Have One Area

When I raise my right arm I have one area (2 " radius ) on the outside of my bicep that gets a sharp pain. I don't remember doing anything that injured it. If I lay on my right side to sleep and put my arm under my head. That is another time it hurts. The pain has been there for 3 weeks. I thought if I pulled a muscle it would have been better by now. Any ideas?