What level of stuffed nose is dangerous?

Hello, will be flying soon and to add on to the already existing fear, I just learned about the possible effects of flying with a stuffed nose. My question is, what would be too much? What's the limit of uncomfortableness before you should cancel a flight? Is a "cold" level stuffy nose ok? Can you take medecine to help with it?
(Of course without considering contagiousness and affecting others)