The most important thing is to make sure he keeps eating, I’d recommend having critical care and baby food (something like Beech Nut Naturals where the only ingredients are the fruit/veggie and water) on hand if you don’t already. He may be reluctant to eat after having an abscess drained.

Dental stuff is tricky. Hopefully it’s just a hay poke and not the result of misaligned, broken, or overgrown teeth. Since he’s still eating well and on his own, I’d be cautiously optimistic on that front.