Sudden upper left arm pain with no injury? 22 y.o female. achy, comes and goes, burns and stings. felt in back and neck as well. osteosarcoma? strain?

Nerve Pinch: This sounds like a pinched nerve in the neck. Although it could be other less common causes. If you have no other medical problems: infection history, cancer history and no significant weakness then give the pain 6-8 weeks to improve. Nsaids can be beneficial (unless you have kidney problems). Talk to your doctor if not improving over time.