Trapped nerve in shoulder, severe pins & needles going down arm now getting constant itchy hand. Is this dangerous?

Not with treatment. This sounds like a pinched nerve in the neck which is most likely the cause of your symptoms. You'll need to get it confirmed by nerve tests by a neurologist. It could be a peripheral nerve lesion (uncommon though) like a carpal or cubital t syndrome with retrograde radiation. The nerve test will help greatly. You might need surgery to decompress it, if nothing helps.