Arm pain can be from a number of things. The arm pain can originate from a neck problem and then cause pain to radiate into the arm or it can be from a tendon, muscle, or joint. The first thing to determine is the situation that causes the pain. Is it weight lifting or something as simple as brushing your teeth?
If the pain is during an activity then changing what or how you are doing that activity can alleviate it. If the pain occurs unrelated to an activity, then you need to see a doctor to determine if it a nerve issue or a torn ligament, muscle or tendon. Hope that helps!