Could he have gotten into anything he shouldn't have?Does he get bones, rawhides or people food?Does he ever eat non-food items (sticks, toys, towels, ect.)?
Any vomiting or diarrhea?
Thanks for answering my questions.
It's not uncommon for exceptionally barky dogs to end up with some throat tenderness from a prolonged barking session. The fact that there's literally no possibility that he ate something that could have poked his throat (like a bone or rawhide), and is eating, drinking, and mostly acting normally makes me think this could be what's going on.
At this point, I think it's perfectly okay to give him another day or so to recover and rest his voice. Try to encourage him to be as quiet as possible so that he doesn't further irritate the throat. If he's still acting painful on MOnday, then you should have your vet take a peek at him, just to be sure that there's not something going on like a polyp or some other vocal issue.
And of course it goes without saying that if he stops eating and drinking, becomes lethargic or has any other unusual symptoms you should have him seen at an emergency vet as soon as you notice any of these problems.
I hope this helps.