How harmful for your health is the pain after shoulder dislocation is put back?

Pain varies. Shoulder pain after a glenohumeral reduction (put back in) is typically less than while it is out of place. For first time dislocations the pain level tends to be higher, but individual tolerance must also be considered. After any dislocation/ reduction you should have an x-ray regardless of pain level to rule out any damage to the bony structures that may have occured during the trauma.
The pain . Is usually significantly improved once the shoulder is back in place.