This exercise will stretch the posterior capsule of your shoulder to improve internal rotation.

Start by lying on your left side to stretch the left shoulder. Flex your shoulder and elbow to 90 degrees with your fingers extended. Drop your hand down towards the bed as far as you can. With your other hand, press down on the back of your wrist for 5 seconds as tolerated and then relax into more range of motion for 5 seconds. If the stretch is uncomfortable, try to bring the shoulder to 45 degrees instead of 90 degrees and progress from there. Repeat 10 times.