It doesn't seem serious to me... as long as she's still behaving as usual, isn't oozing, swollen, or tender in that area, or losing more scales, she is probably fine.
My tort has always had a tiny spot on her head but it's like a burnt orange color. (I call it her bindi. ?) In her case, Vet said it's likely an injured scale from the past and though it'll never regrow, it isn't a problem.
To me it looks like just the opposite of what Black dog has said. Looks like a scale that's lifting and getting ready to shed. At any rate, it's nothing to worry about.