Ive been a very serious lifter my entire life. Shoulder injuries/tendonitis come up a lot in the gym. It’s typically going to be one of three things:
1. Rotator Cuff (minor tear or tendonitis)
2. Bursitis
3. Labrum tear
Hopefully it’s not the last one. If it’s one of the first two, get yourself some resistance/rehab bands. Theyre just thick latex rubber bands in varying strengths.
Tie one of them to a doorknob in your house that you walk by a lot. Youtube “rotator cuff band exercises). Every time you walk by the doorknob, do one of two of the exercises until you get a deep burn in the area being worked. (Not pain just muscular fatigue). Itll strengthen the muscles, meanwhile pumping blood in and causing healing. The more you do, the faster itll heal. Do NOT ever get a cortisone shot or wait for healing. Active rehab is the way out.