I would definitely recommend that you make an appointment with your primary care doctor
to discuss this issue. Any persistent pain or other symptom that does not go away should be investigated with your doctor' help to make sure that there is nothing serious or treatable.
Your doctor should be able to tell pretty quickly whether or not the ball in your back is due to a spasm or soreness inside the muscles in that area or if this is actually a growth under the skin.
If this turns out to be a muscle spasm, then it is probably from tension and overuse of the muscles in the shoulders. In addition to anti inflammatory medications, your doctor may prescribe some gentle stretching exercises or may send you to a physical therapist
. More severe acute cases of muscle spasm may also require muscle relaxants.
If, on the other hand, this turns out to be a growth under the skin, it may need additional investigation. Most growths under the skin are benign (not cancerous), however some can be cancerous. Therefore, based on what the growth looks and feels like, your doctor may recommend that that you have the growth removed by a surgeon