Mine had similar issues arise. Hard to get rid of unless you take time off. Her cause of muscle imbalance in the upper back and bad posture. What helped aleve her pain was PT twice a week, naproxen 2 pills x 2 a day, days off of pitching (inning limit), ice not heat to help with inflammation. She massaged it daily with a massage gun/lacrosse ball on the knot to release it even it is temporary. But rest and targeting muscle balance on chest and shoulder/back seemed to help her. Then it was all about maintaining. Each kid is different as she said heat flared it up.My daughter is 15, she plays travel ball and I coach. Recently she has been experiencing pain in between her shoulder blades closer to the right side just above it. It feels like a knot of muscle. Has anyone heard of this or experienced it? I’m certain is something she’s doing mechanically