3yo picks at his toe nails til they are sore/bleed

[GlitteryFluff]

Just that really.
3 year old Ds keeps picking at his toe nails/skin around his nails/ pulling bits off, til they're sore/bleeding. It looks like he doesn't have any nail left on one toe. I keep socks on him as much as possible hoping if they're out of sight he'll stop but he just seems to whip them off and does it. It seems like a habit.
Anybody else's dc do this? Did you manage to make them stop? What did you do?

Bumping.
He's still doing it and also doing it to his fingers too.
Anyone else have this with their dc?

Mine does this to his nails too. It’s def a habit - have no idea how to make him stop!