Hello, I'm Dr. Deb and will do my best to help you today.
I'm sorry for this concern about Kona.
There could be several possible explanations for the swelling that developed so suddenly:
--it could be an abscess
--it could be a hematoma (blood filled space) or
--it could be a seroma (serum filled space.
The last two are commonly secondary to trauma.
Regardless, this is not something where you'd have to rush her into the ER especially since she's not bothered by it. Waiting until tomorrow will be fine. More than likely, your vet will aspirate fluid to see what they're dealing will and then will go from there as to the best way to treat it...at least this is what I'd do.
I hope this helps. Deb
Thanks for the rating; it's greatly appreciated.
And, best of luck with Kona. Kind regards, Deb