What Could Collar Bone Swelling Post Shoulder Injury Suggest?

Fell down the stairs, bruised my lower back, and hurt my left shoulder. Age 23, height 5'7, weight 113lb. Now I can't move it without pain. There's very minor swelling around my collarbone-shoulder attachment area, but no signs of any bones sticking out or anything, like was noted with some shoulder injuries-- what do I most likely have?