Severe Pain / Ache in right Shoulder!?

Last night I woke up with an aching in my shoulder that was pretty unbearable. I had to get up, and eventually managed to get back to sleep through a combination of applying heat to it, taking painkillers, and also being very very tired. The pain was centred in the shoulder and constant, although was occaisionally spreading down to my forearm or up into my neck. Presumably I managed to pull or tear something whilst sleeping awkwardly. I still had the normal amount of movement in my arm, it didnt feel stiff or anything, but the painw as constant, there was no position I could put myself in that made the pain worse,, or better unfortunately. So now its the morning, and my arm doesnt hurt anymore. But, last night while I was browsing the internet trying to find a way to ease the pain, it seemed most sites suggested that this pain would not be a one time thing, and that it would be best to see a GP. Now, I know better than to believe medical advice I read on the internet, but I would like to have the opinion of someone else as to whether or not I should get it looked at. I wouldnt really want to have to sit through that pain again, but my plan for the moment is to see whether it comes back or not and if it does see someone about it. When I googled the symptoms it seemd that the most popular results were either articles on something that I think was called a rotator cuff, or something along those lines, or a crushed nerve. I guess it could also be cramp, but it lasted way longer than I thought cramp could. Anyway, any advice would be greatly appreciated. Thank You.