Vegans can eat their own boogers. Their whole disposition is on the basis of ethical consumption and consent. A cow can’t consent to being milked. We’ve bred them and in a vegans eye’s, exploited them for so long that, that’s just the status quo. Similarly bees collect honey to feed themselves. They don’t understand we take what we deem is a surplus to them. So they never consented to share with us.
If you pick your own boogers, you consented to do so. That means it’s ethical to eat.