7 yr old Goldfish lumps

Ok, so this is a weird question. My fiancé has a goldfish that is one of those goldfish won at a fair, almost 7 years ago in July!

Bauer (the goldfish) started with a tiny bump on the top of his body in 2022. Since then, it has grown ENORMOUS. Just this past week, the bump/lump is now growing its own bubbles? What is this?

He is eating and swimming normally, and other than looking horrible, he doesn’t seem to care about it