I think part of the problem lies in the fact that your son is so young and really doesn't understand what's happened to him.
What's done is done, so I don't think it's worth the energy to wonder if it was a mistake.
I think your little guy is afraid that anything will hurt his throat and he's probably wondering if he's always going to feel the way he does. Little ones have no concept of time or days, they just know they don't feel well and they get tired and cranky. Of course, if he's not back to eating and drinking regularly, that will lend to the crankiness too.
Keep in touch with the doctor. Try giving your son some warm things as opposed to cold. Perhaps some warm custards. My kids always liked warm Jello when they had a sore throat. You add warm water to let the Jello dissolve and sip it. Avoid flavors that are red so that the coloring can't be confused with inflamation. Maybe try some warm white grape juice or gatorade.
Hang in there. Hopefully in the long run, getting this over and done with and out of the way when he's so young and won't really remember much when he's older will turn out to be a really good thing.