Swelling behind left ear with pain running down left side of neck into back. muscular pain in full body especially left bicep. what would be the cause of this?

Exam needed: Swelling and pain behind the ear may be from an inflamed lymph node,infected cyst or infected ingrown hair. A physician would have to examine you for diagnosis and treatment. Generalized muscular pain would appear to be a separate issue such as autoimmune disease, neurological or muscle disorders and a rheumatologist is best to evaluate your symptoms. Appropriate testing will be done.