I think that sometimes a really bad smell can damage your nose hairs, or whatever is in your nose which registers smells. It's a bit like after someone flashes your eyes with a really bright light and you can see it for a while afterwards 'cos your eyes got damaged, or you hear some really loud noise and your ears ring and you can hear it for hours afterwards.
I notice that when I run over dried doggie doos with the lawnmower and the smell rises up in a white fog. You can smell it for hours afterwards even though it is long since gone.
Same thing when you tread in a fresh one.
Even tho you wash it off your foot you can still smell it for hours.
It's because the nose hairs are permanently bent from the initial impact.
Well that's what I recon anyway.