It is best that you have your shoulder assessed by a sports injury doctor for proper diagnosis and treatment. In the meantime please follow these simple techniques you can do at home to address pain. We call it the RICE technique:
I= Icing. Apply ice packs for 20 minutes to relieve pain
C= Compression. Wrap your shoulder with bandage to control swelling
E= Elevation. Raise you arm to allow for blood and fluid circulation.
As much as possible avoid using the affected side when lifting a load. Do some simple range of motion exercises.