He's probably crankier and is having a hard time having food in his mouth since his nose is probably stuffed up. He can't breathe around it.
Check out Super Baby Food by Ruth Yaron, by the way. Very, very helpful!
Just go with the flow, leave it "off the table" - sorry for the pun - and follow his cues. When he is happy and back to his usual self, start eating something in front of him and see if he gets interested. Then you know you can put him back up in that high chair. But whatever you do, don't pressure him. Like Yaron says, no matter what happens, smile and say "Mmmmm!"
If he doesn't agree, smile, say, "ok!", take the food away and let him down. No pressure.
L.