Two days ago I was adjusting my position in a car seat and heard a loud pop from my back and shoulder. Earlier that day I noticed that I had what felt like a muscle knot in my upper chest (right side). After the loud pop, the pain concentrated in my upper shoulder area. I began having a burning sensation in various parts of my chest, and now have patches of a rash that look like poison ivy, but they're on those same places on my chest that were burning the day before. I also don't recall touching any poison ivy recently. Are these symptoms related? If so, what should I do? I'm afraid the rash is getting worse.