There is a reason for the painful “knots” you get in your back near your shoulder blades. The reason is that you have muscles pulling on your shoulder blade. That causes your shoulder blade to pull the muscles on its’ other side. The muscles that are being “pulled” on become taut (a kind of tightness) to protect themselves. That tautness is the “knot.”
So, what muscles are pulling on your shoulder blade, and why?
If you are right-handed, you probably have that hand and arm in front of your body a lot, writing, mousing, or doing other similar work that requires your right hand. Is this correct?
Being in that position, with your arm and hand in front of your body for long periods, causes the muscles on the front of your arm and chest to become short and tight. They get short just because you are holding them in a shortened position and they get used to being short.
Also, you might also be dropping your right shoulder for one reason or another. Maybe, the position of your desk causes you to tilt, or maybe you prefer to scrunch up on one side of the couch (sofa) all the time, or maybe you sleep on your left side most of the time. All of those things will cause the muscles on the right side of your body between basically your shoulder and waist to shorten.
So, now you can see that you may have muscles pulling on your shoulder blade from at least three places: (1) the muscles in front of your body (your shoulder blade attaches to those muscles near your collar bone) (2) the muscles on the outside (lateral) side of your shoulder blade (under your arm pit and on your ribs) and (3) the muscles below your shoulder blade (back and rib muscles.)
Those are the muscles that must be released first.
Manual release (massage) of the pulling muscles makes the process go faster than stretching alone, but if you will stretch, that will also help correct your problem.
The stretching movements are primarily to move your arm up (over your head) and outward (to open and stretch your chest muscles.) You can stretch both sides, but the shortened (symptom-side) muscles need to be stretched 4x as much.
Also, if you strengthen the muscles between your spine and shoulder blades, that will help correct this problem (because the spasmed muscles will be more able to “hold their own” when pulled on.) And, strengthening will also help prevent future pain.