Any massages therapists out there? Or knowledgable people about muscles?

So I'm 11 weeks pregnant and me dr said no hot baths, but i have had a muscle knot in my left upper shoulder. It has hurt but it's been manageable. But today the pain is spreading to a horrid ache that radiates from my elbow to my pinky. My mother in law who has muscle knowledge says its related to the knot in my arm and when I get it rubbed it definitely affects the arm. But she doesn't know if a heat wrap in my arm will do me any good. Since the problem is in my back I am unsure if a arm wrap would do anything but it hurts like a s.o.b.