What Could Pins And Needles On Hand, Arms And Elbow Suggest?

I have had pins and needles in my left hand for about 2 weeks now. It seems to have travelled up my arm to my elbow and today feels like it has travelled to my arm pit and have pins and needles all the way down my arm to my finger tips (inside arm, not outer). It feels weird - please help me to diagnose the problem.
Thank you