What causes chest pain, sharp, stinging nerve-like pain in upper left chest extending to abdomen? brief but strong, occurring over last 3 days?

Atypical: Could be early shingles, costochondritis, a pulled muscle, etc its very atypical and would be fairly confident its not your heart.

Causes and mechanism: Many potential causes of such symptoms but the same mechanism -- when the chest pain is sharp and fleeting, stinging or electrifying, can be at varying intensities -- it is caused by irritation of the nervous network in the chest wall. The nervous system is rather like the body's own electrical system -- so the sensation is indeed electrifying. The most common cause is a simple chest wall strain.