Hurt shoulder when wrestling?

The other night i was wrestling my friend and remember getting slammed really hard on my back. i didnt have any sudden pain, but when i woke up in the morning my right shoulder and chest hurt. My chest felt like i had pulled the muscle and i had a sharp pain in the middle of my shoulder blade. It has been a week and the pain has decreased but i still feel it when i exhale hard or laugh. i am hoping i have just pulled a muscle being that the pain is not too horrible. how badly does ligament damage hurt? and how long should i wait for the pain to go away?