When you are talking to a patient as a doctor or while asking a friend what is the difference between "have you got a runny nose?" and "Is your nose running?". How do you choose which one to say/ask?
You might have a "runny nose" (which means that, as a result of a cold or nasal infection, you tend to have lots of liquid mucus) but right now your nose isn't running (no liquid is dripping from your nose). A runny nose might last for a few days. But your nose won't be running for all the time.
The solution to a running nose is to use tissue or a handkerchief.
The solution to a runny nose might be to carry a handkerchief, or you might use a decongestant or try steam inhalation.