My cat had a runny nose and now its stuffy why?

I went to my vet and told him my cats eyes were watery and he's been sneezing and has a runny nose and he told me he has a kitty cold (a URI) he said it was normal and he gave me amoxicillin. My cats been taking the amoxicillin for a few days now and he's been acting a little better but now his nose is just stuffy i can hear him breathing it kinda sounds like snoring...is this a bad thing??