I Am Having Pain In My Left Shoulder Area That

I am having pain in my left shoulder area that radiates down my arm to almost elbow. It started 8 days ago..no injury known. Left arm has no strength for lifting straight up or side to side. Doc gave me pain med and then this week added prednisone. He thinks it may be a pinched nerve in my neck. The pain is not receding. I worried about long term damage if it's a pinched nerve. Any advice? The doc is general practice..thinking I should see specialist. He mentioned a nerve study?