Hi I have pulled a muscle in my upper right arm under my back bone. Is there anything I could do or take to help?

First of all, you could apply some Atrogel to the area. This is made with Arnica Montana flowers and brings relief from aches and pains. 

Other than that it may help to apply some heat to the muscle – hot baths and even a heat pad will help to relax the muscles and, in turn, ease tension and pain. 

I'd also recommend you keep moving to avoid stiffness and aid healing but don't do any exercises that are too strenuous at this time - things like walking should be sufficient.