If you are in a hurry, and you only have a few minutes to exercise your shoulder, here are my top 3 shoulder exercises. You can use weights or resistive bands. For a light weight, you can use a can of soup or vegetables.
Lie down on your side with the injured side up. Keep your elbow bent to 90-degrees by your side. Start with your hand at your stomach, and slowly bring it parallel to the ground. This is shoulder external rotation. Start off with 10-15 and work your way up. Then switch sides with the injured side on the ground for the second exercise. Still keeping your elbow bent, and by your side, start with your hand on the ground, and slowly pull in up towards your stomach. This exercise is shoulder internal rotation. The third exercise is going to be rows. Get up on all fours, or quadruped and straighten out your arm. Pull your arm up with your elbow bent to 90-degrees and close to your side. Squeeze that shoulder blade, or scapula up and in towards the middle of your body.