Help! Weird red growth on guppy

[Kyy]

Hi! I’ve had this guppy for almost 2 years, it had a small red dot on its tail when I got it, it’s slowly been growing but never seemed to effect him or spread to other fish. But now it’s so large and I’ve noticed today that his scales seem to be raising. I’m really worried about him and my other fish. It’s a lumpy, very odd looking growth on his tail fin, it almost looks like the fuzzy red bulbs on a sumac tree