Hard to evaluate something like this from a post, but I'd say you'd want to consider seeing a doctor/chiropractor if your symptoms don't subside or improve in a week or so. If it were me (again, not a doc), I'd try taking some anti-inflammatories for a few days (Aleve is a good one!) and icing that spot.
If the symptom is produced only during certain movements, perhaps you've got a subluxated (misaligned) vertebrae or something of that nature (chiropractor would be a good route).
Have you tried foam rolling your thoracic spine (upper back)? Simply get on a foam roll, laying on your mid-back facing the ceiling, and give yourself a 'self-hug,' then roll up toward your shoulders. This may help stretch tight muscles, etc.
Note - Don't do biceps thinking you are resting your back! my form was awful w/ curls (not noticeably in the gym, but when discussing my 2 year nagging unilateral, rear shoulder pain w/ my PT, he pointed out that my shoulder blades were winging out like a Teradactyl going in for the kill, when I set up for standing curls, rather than keeping a tight core and keeping my shoulders back and down... something that sounds easy, until you are working those last few reps or going heavy weight... years of crappy body english and bad form can be hard to undo.). *just my experience.