Thank you for your query at DoctorSpring.com
I have read your query with diligence. After going through your x ray it looks that you may be having avulsion of periosteum over the acromion bone of shoulder, it means there is associated injury to rotator cuff which is a muscle of shoulder. At present you should keep your arm in pouch arm sling.
You may also have a MRI investigation to rule out any other injury.At present, you should do cold fomentation over your shoulder & take a good analgesic like Ibuprofen for relief.
Feel free to discuss further,