I'm glad to hear that though I wouldn't continue to do it, it causes anemia and gastrointestinal chemical burns.
He's acting normal other than the runny beak?
It could be an allergen if he is.
I would hold off on giving him antibiotics, natural or otherwise unless it's obvious he has an infection.
I'm very sorry, if he starts getting listless, you need to find someone to put him down or prepare yourself do it yourself, that's likely more than enough garlic to kill or cause major issues. Hopefully it was only a small clove and he's a big boy, so he'll pull through.
If he lives through the...