What Causes The Arm To Hurt When Lifting?

I am 27, 170 lbs, 6'. i was playing softball and dove for a ball to the left. My arm was fully extended when i touched the ground. i landed on my left side about armpit/elbow level touching the ground first. Since then, I cannot lift my arm higher than my shoulder and if i try it hurts on the top side of where my arm meets my shoulder. it does not hurt when i bring it back down. I can bring it back and extend without discomfort. I can extend it forward however there is a feeling of some resistance. It feels somewhat fatigued when relaxed. All other functions seems to be normal. I have never had any pain or problems with my shoulder or arm before. It has been almost 2 weeks now and I've had no progress in comfort or movement. Please advise if this is something that sounds like it coulld require surgery or just additional time resting it?