The shoulder area is a common place to get trigger points, aka muscle knots. Trigger points are basically when a specific area on a muscle gets irritated and tightens up into a ball or knot. These stretches and exercises may help relieve shoulder pain and soreness from muscle knots and trigger points.
Starting off with shoulder circles and shoulder (or scapular) squeezes will help get the muscles moving and warmed up.
Next, stretches like the upper trap and levator scapulae stretch will help relax and loosen up the muscles to help release the knots.
Finally, if the stretches are too difficult or maybe you are on precautions to not do those movements, a ball can be used to put pressure on the trigger points directly. A little pressure goes a long way, but too much could irritate it more.