This particular situation is actually quite common and in my experience it is quite common this time of year (late spring and early summer). However, most folks that suffer from this will right it off as a tight or strained muscle. Unfortunately, doing nothing will yield similar results and the pain between their shoulder blade and their spine will persist. (NOTE: this can also occur at the joints where the ribs meet the sternum (chest bone))
In my video below I explain what a “rib out” is, where you will typically feel the pain and what movements will provoke it. I also tell you what to do to get quick and painless relief.