Yikes.

Delayed allergic reactions aren't that unusual - when I get my allergy testing done, the nurse always re-checks the wheals 24 hours later. For me, also, circulation in my hands and feet isn't that great, so if I get a sting or bite on a finger or hand, especially, working with my hands will mechanically spread the venom around and make the swelling worse.

But yeah - I'd keep an eye on it for sure, maybe even pop into urgent care tomorrow rather than waiting for Monday if it hasn't started getting better.