It sounds like a series of spasms from holding your arm in that position. It could have irritated a nerve. I have had that happen to me and it is not comfortable at all. I had to use lots of heat, then massage from DBF or DDs, and then ice to get any minor relief. I finally got desperate and decided to try the Salonpas that MrsD mentioned. I did the heat, massage, ice routine and waited about 20 minutes and put the Salonpas on the area, took 2 Advils, and then went to bed. By the morning time the spasm finally released some and I was able to move my arm and head more.

Hope you are feeling better.