IMO....the amoxi will do him just fine, at least for the next few days, it should decrease in size but if not than may need to be drained, but I think you are safe with the antibiotic and wait and see over the weekend.....good luck♥
I agree w/ Opus. The amoxicillin will be enough. Just keep your eye on it, like I know you are. I would also call the vet just to keep them updated.
Please keep us posted and let us know how Oliver is doing.