The symptoms of left neck tendon pain may be due to the following reasons: 1. The symptoms of left side neck pain may be caused by pressure on the nerve roots due to cervical spondylosis. 2. The symptoms of left side neck pain may be caused by soft tissue injury to the muscles or ligaments on the left side of the neck, as well as fasciitis and ligamentitis. 5. The symptoms of left side neck pain may be caused by aseptic inflammation of the muscles, ligaments and fascia due to strain or trauma or cold.