Bump on my cat's upper lip

Hi everyone,

I’m posting here because my cat has had a small bump or lump on his top lip for the last few days.

It was quite subtle to start with, but it seems to be swelling a bit more every day. Despite this, he’s eating and drinking as normal, his behaviour is fine and he doesn't seem to be in any pain when I gently touch the area.

I’m just wondering what it could be: a sting, irritation, a spot, an infection or something else?

I’ve attached a few photos taken today. If anyone else has dealt with something similar with their cat, I’d be really interested to hear your thoughts and feedback.

Thanks in advance for your help 🐱