Shoulder muscle in painnn!!! What to do!?

My left shoulder near my neck i guess huts and kinda stings. I can only put my head slightly to the right and if i try to straighten my neck or head, it would hurt so my head tilts to the right again. What should I do? And how should I sleep? Tilting my head back also hurts so either it's neck muscle pain or the muscle closest to my neck. i actually can't tell where it is at the moment but it HURTSS.