Or you could have pulled something in your neck back or shoulder. I pulled my tendon once on the left side of my back and my whole arm was numb and tingled. Had a massage and she worked on it for an hour and it was out.
Another time I pulled my shoulder out and my arm did the same thing but only to the top of my shoulder my hand and fingers. Took 3 massages to get it fixed that time.
Do you work out of have a job tht require you to work your upper body alot of keep your back stiff like a desk job or something like that? If so then then stretching can help you out greatly if you do not have the time or money to get a massage done.