I've had this non stop pain under my left shoulder blade for three days. i also get a tingling sensation every now and then.

Muscular?: What kind of activity do you do.? Could this be related to martial arts or some type of running or exercising type of activity. If it has persisted this long and continues to be bothersome I would call the doc and see if an appt is available. Does not sound serious but can get treatment that may be helpful Must also consider pleurisy that is not related to muscle but may be an infection in chest.

Activity: certain over shoulder activities like painting walls, redecorating can cause issues with the shoulder girdle call "thoracic outlet syndrome" where overusage causes the muscles to swell and narrow the space where the nerves exit causing pinching and symptoms similar to yours. initial study would be a simple chest xray.