That is something an X-ray will have to tell you. but if you can't move it and it feels stiff, but your not in terrible pain, it is probobly just a sprain. Either way you should go see a doctor to check it out
Symptoms of shoulder sprain may include: Pain, tenderness, and swelling around the shoulder Redness, warmth, or bruising around the shoulder Limited ability to move the shoulder and increased pain...