Hi there, and thanks for this question.
If he is known to be a Herpes virus carrier, it is quite possible that this is a flare.
As well as steam, it helps to ensure the air is generally well ventilated and free of dust, smoke and cooking fumes.
We should also clear away any nasal discharge with warm, wet cotton wool as needed.
Other considerations for his signs would include an oral issues (such as stomatitis or a dental abscess), an allergy, a nasal polyp or a new infection. So if signs are not improving, a check up is sensible.