Instead of heading to ER, better head for an ortho. It is clear case of cervical disc syndrome or intervertebral disc prolapse of cervical region. IVD space reduced, reason may be trauma, degeneration etc, emanating nerves compressed and pain radiates to shoulder. Some traction may be given for few days. Cervical collar for support may be given. Few physiotherapy exercises after pain subsides. Some pain killer 1 sos may be necessary some times. After you recover from acute phase, learn Yoga postures, for few minutes practice a day and live comfortably after. Hope it helps you.