Bump on 5yo son's lip, what is it? Pics included.

This lump has been there for about 5 days now, he says it doesn't hurt unless he's eating but only sometimes. He also told me it's not really bothering him. It doesn't look like a sore or anything and appears to be getting taller, if that makes any sense? Could it be a Mucocele?

Any idea is appreciated! Thanks!