could be a tendonitis. any pain requires seeing doctor. workouts shouldn't be painful to the degree that you feel like the pain is a possible injury plus you don'yt want to take a chance tearing your bicep muscle. I'd stick with a lower weight until diagnosed by a doctor or even a physical therapist/athletci trainer. Might seem a little inconvenient but worth saving an injury. I'm a cert. personal trainer and would hesitate to train anyone with the symptoms you're having in your arm. Who knows it might be something as simple as working the smaller muscles in the arm and requires some stretching but def. seeing a professional is a good idea.