He needs a doctor. This could be several things but no one can diagnose without examining him. Some of the possibilities are quite serious (like threatened stroke or heart attack) and some of them not so. Don't mess around with this.
Numbness. Numbness of the arm can range from nerve impingement from an injury, to a stroke, to a chronic neck and upper back arthritis or injury. Part of the evaluation should include a full neurologic evaluation and possibly radiology of the neck and shoulder. Treatment options include anti- inflammatories, physical and massage therapy, and sometimes muscle relaxants.
Paraesthesia. Numb, tingling sensations in an extremity are called paraesthesias. They are usually the result of compression on a peripheral nerve, either as it exits the spine or somewhere along the course of the nerve. He should be seen by a physician and may need further diagnostic studies, such as MRI of the spine or nerve conduction velocity studies.