I think your symptoms may be due to nerve irritation in the cervical (neck) spine because of cervical disc bulge. This pain may be referred and perceived as occurring in the back of head & shoulders (as it blades)- LHERMITTES SIGN, arms or chest, rather than just the neck. Other symptoms may include vertigo, nausea (dizziness) and stiffness. It will be best that you consult a neurologist who would like to prescribe Pain killers, steroid and muscle relaxants. Other treatments could be cervical orthosis such as a soft cervical collar or stiffer neck brace to restrict neck movement till you get complete recovery. In addition, cervical traction may also be suggested by the doctor, if condition is severe. Hope this helps.
Oops, typo, meant injure vs injury.
When did he injury the shoulder?
Sounds like a pinched or an inpinged nerve.
Has he tried ice, naproxen/aleve and rest?
If this has been going on for more than a couple of days, he needs to seek medical attention.