I got a shot in the arm a few months ago and my arm is still sore?

Probably OK: This is unusual but not unheard of. Sometimes there is some trauma to the tissue of the arm, or maybe a nerve, that just takes many months to heal completely. If it is generally getting better, you might just give it some more time. If you are concerned, or it is not trending better, you might have your health care provider take a look.