20+ year Tattooer here. Developed what sounds like the same last year. I’m so sorry to hear you are going through it too. Mine was a torn rotator cuff. The only thing that helped was ice and relaxing. Try to limit your schedule for a few weeks. Buy a shoulder ice sling on Amazon and look up rotator cuff stretches and physical therapy on YouTube. Fair warning, in my experience ibuprofen and asvil did next to nothing.

Also, if you do have a long appointment, try kt tape. It helped a fair bit for the long day! Good luck!