I wonder if it could be a trigger point or rhomboid stress/strain?

the rhomboids are located under the shoulder blade towards each side of the spine.

They can easily get strained if shoulders are forward a lot, like with computer use, knitting holding books etc. to fix it we need to be aware of head/shoulders posture, not being forward of the body..


triggerpoints can be checked with a tennis ball or other object like it.
press/roll it against a wall or on the floor looking for very tender spots in your back.

If you find any hold the pressure til pain fades away, then do some stretches to work it out fully
TrPs may come back or more may appear if they were latent.

HTH..