Lump on dogs back

I have an appointment for her on Friday but has anyones dog gotten something like this before? She’s had a lump there for over a year, I had it checked last year and the vet told me it’s nothing to worry about but it’s gotten bigger just since last week (from what it looks like anyway) and she tries to bite at it. It looks like it got cut idk if she did it or if my grandfather accidentally scratched her. But there is dried blood around it. This is the best picture I could get. She hasn’t been acting any different just sometimes she’ll try to bite at it