Pain under the shoulder blade can actually be coming from other areas of the body such as the; gall bladder, heart, aorta, fallopian tubes, abdominal organs, diaphragm, and lungs. It could also be from a rib or thoracic vertebrae that is restricted and not moving properly. Tight and aggravated muscles can also "refer" or send pain, numbness and tingling to other part of the body. This is often called a trigger point. An aggravated muscle could be sending pain to this area. See your physician if this symptom persists. As a massage therapist there are several muscles that I would work on to improve this situation provided that there were no medical conditions associated with it.