Nasal Odor

I've recently started dating this guy.  He has this sort of bad breath odor, like the smell of rotting food, that seems as though it is coming from his nasal passages rather than from his mouth.  He has admitted to me that in the past he had been a cocaine addict, however, he didn't tell me how long he had been an addict nor the severity of the addiction.  I'm curious as to whether these two things could be related.  Almost as though maybe the cocaine has eaten away so much of his membranes in his nasal passages that food is getting stuck in his nasal cavity?