What Causes Patch Of Painful Red Bumps On Shoulder Blade?

Hello, I noticed that I had a patch of red bumps on top of right shoulder blade and its painful and the pain is in my neck on that side as well as on the back side of my shoulder. Just noticed last night after dinner. It is the only area that had these bumps to show up. There is no pulse but its just that they are there out of nowhere and its painful, the area around the bumps