Question
It seems every time that I am three weeks into getting back into working out I get pain in my upper right back near my shoulder blade.  This time my right arm seems weak and my fingers on my right hand are tingling.  I think that I have pinched a nerve.  I stretch before and during working out.  Is there anything that I can do to prevent this and can I keep working out if I can stand the pain?

Answer
I do not think that working out through this is such a good idea, it can cause more damage.
I would find a Chiropractor and have him or her evaluate the condition.
If it a nerve related injury, A test called a NCV and EMG can determine the location and the extent of the injury.
When you experience tingling in the hands and fingers it usually is the result of either a cervical disc problem and or a brachial plexus injury.
Do your self a favor and get checked out by a qualified Chiropractor.