Is he on coconut fiber bedding? Because it just looks like a small bit of it may have gotten caught in his lip to me.


Definitely keep an eye on it. If there is any swelling that starts or it worsens, get to a vet.
He's young, so he might of just gotten some substrate caught while eating. Or exploring. Or a small scab if he's been rubbing at the lid a bit. Keep an eye out for that.
But it doesn't look too bad. Just pronounced because it's on an all white snake.