I could be way off, but it kinda reminds me of the beginning of molt lines. I know sometimes a bunny’s first molt is pretty intense and they can end up with some crazy molt lines or bald patches. Although, to be fair, my buns who get molt lines on their face usually get it around the nose, not on it.

Are there any other animals in the house that could have perhaps scratched him across the nose, leaving a bit of a line like that?