Creamsicle was sneezing for a couple of days a couple of weeks ago. She’s fine now, without going to the vet. If Sam isn’t better in a couple of days, I’d go back to the vet rather than to wait until Friday.
How old is he? The important things eating and drinking. If he’s still doing both and doesn’t show signs of any other problems, I think it would be safe to wait it out. Just make sure to monitor his food and water intake. Sometimes kitty viruses can take awhile to run their course. I hope he feels better soon!