How to treat severe upper back pain left side?

Neck and back pain. The back pain can be caused by many issues such as muscle strain, spinal stenosis, ruptured disc, nerve impingement ... If you pain is severe, you should seek medical care as soon as possible for appropriate evaluation and treatment.
Severe back pain. Anytime i hear severe, i would suggest a physician evaluate. Regarding the location, pain upper left (near shoulder blade) can suggest muscle spasm/tendinitis of shoulder, thoracic spine/disk problem, lung/heart disease, stomach/pancreas/spenic disorder. Seeing an md could help to determine the actual location and determine appropriate testing to get a diagnosis. Too little information.