My left shoulder has been injured for a while. i feel muscle tightness in my neck and surrounding area, and range of motion is restricted. what to do?

Physical therapy: Warm soaks & Ibuprofen for a few days to help pain. Physical therapy and exercises as advised by them

Rotator cuff injury: you may have avulsed a tendon or injured a nerve you need to be checked by the orthopedic doctor

NSAIDs and therapy: You can try ibuprofen and physical therapy. Get a physical therapy evaluation and then you can continue proper exercises to improve your shoulder and neck function into the future.