I have had a tension/mild soreness/ache in my left shoulder/neck for the past 10 years, starting with a sneeze on a bicycle. how can i fix it?

Eliminate the pain: First thing is to try to determine cause to check for any fracture, calcium deposits with xrays and medical checkup with bloodwork to look for arthritis/gout. If it turns out to be muscular/tension/bursitis of shoulder neck, then first eliminate pain with ice packs, antiinflammatories, rest and after pain relieved begin physical therapy/myofascial/stretching and finally strengthen muscles.