What is this bump on my kitten’s nose?

I recently adopted this 6 month old kitten and noticed a slightly raised bump on his nose. I’ve been monitoring it for two weeks and it seems to have grown over the past week. What could it be? No fluids or blood coming from it and he doesn’t seem bothered by it.

We had a vet visit last week, he said it was probably a play injury caused by my other cat. (He didn’t seem too confident in this statement)

Image: https://imgur.com/a/eS9Xkw5