It's probably a stiff muscle/s sqeezing your nerve bundle. You need to relax your shoulder, put some hot pack (or take a hot shower). It should get better within 1 day, if not, see a doctor.
A week ago, I woke up because I was feeling a tingling in my palms and little bit of loss of feeling in my pinkie, so I freaked out. Well my mom told me to do the hotpack/hot shower, feeling in the finger came back quick, and pain in the shoulder slowly went away after a day or 2. I guess the things inside the shoulder slided back to their right position 😛