I got hit in the shoulder, and now i can't raise my arm up all the way. what kind of injury is that most likely to be?

Contusion: Given your age likelihood of sustaining a rotator cuff tear or other significant injury unlikely unless fairly high energy mechanism of injury (car accident). Therefore I would guess this represents contusion or bruising of soft tissue and should improve with time and simple measures like ice, anti-inflammatories and activity modification.