We trimmed the horn of one Swaley tup ourselves, thinking, from feeling for warmth, that it would be only dead horn we were removing. Wrong, it bled profusely and the tup clearly felt it. Not only that, he never forgave us, and we’d turned a previously well-behaved tup into a menace.
So unless it is really very obviously only a dead inch or two from the tip you need to remove, I’d recommend the vet.
It’s very common in Swaledale tups to need one or both horns trimmed right back at some stage. No one seems to bother about it as a breeding selection criterion, sadly.
Blackface tups usually have their horns shaped by a professional, so that the problem doesn’t occur - but it’s not through breeding, it’s through intervention earlier on when the horn is still somewhat pliable.