shoulder problem

my shoulder hurts ...its like a grinding pain..i guess it could be muscular but seems to me like its in the joint like the joint is dry or something. for example, if i were in a seated bench press position arms out to my side at 90 degree angles palms to the floor, and i rotated my elbows up sends a severe pain into the joint of my shoulder. i hope that was descriptive enough. just wondering if anyone knows anything about it, or what i can do about it