So I’m 17. For a while now a spot on the side of my upper back has been sore/feeling irritated. The best way I can describe it is that it feels like a sun burn. But my back looks completely normal. No red, rash or lump, nothing. It just feels irritated to touch/ rub. I have no idea what it is or what caused it and I’m really worried it could be something bad like arthritis. Help me!?