I have a very painful sore between my right shoulder blade and spine , specifically underneath that muscle between the middle of that shoulderblade and spine. It has lasted for 4 days now, and it is followed by a needle-like sharp pain that come every 30 second. I have full range of motion in my arm , and it does not hurt when I breathe or move it. I have no pain in my chest/belly or anywhere else, but I do have a chronic sinus infection if theres any possibility of that being a cause. The soreness part of the pain feels like a cramp mixed with a knot.