Probably juvenile warts (papilloma). Are there any anywhere else?
They don't always have to be youngsters to get them - my horse got a bunch of them on his muzzle, aged 14! He was turned out with a yearling who had them and I guess that's where he got them from, probably hadn't had them as a youngster himself.
Big sigh of relief thanks everyone 😊 yep that's the only place he has them, don't want to irritate them anymore so I'll let them run their course 😊