I can only speak for myself but when I had a similiar situation (right between shoulder blades) where I was always scratching against the wall, and I think I was doing that for 2 years. Finally when I was at the doctor (dermatologist doctor) I figured I would ask him since they are the experts with this type of stuff. He said he did see something there but thought it was nothing but did a biopsy anyways (dont panic hearing that, its normally always nothing and its just a small shot and he cuts a tiny piece off, you dont really feel anything other then a simple shot). Its literally done in seconds.
He told me its common to have an irritated mole that itches like this. It could also just be dry skin. Eventually 2 weeks later they told me it was nothing. The itch on my back is now gone lol. I guess they shaved it off so that fixed that also. You dont even need stitches or anything like that because its almost like a shaving cut and band aid is all you need.