What it smells like?
If it’s kind of vinegary than this is known to be one of the candida symptoms and, in my experience, it could get worse during die-off. My experience also is that it also happens when you eat something that you should not, meaning you are feeding “the beast” (candida).
I had it before the treatment at times, but my nose was stuffed up all the time (which now it isn’t anymore so obviously it was related to candida) so I could not smell it all the time. My nose mostly is not stuffed up and I can breathe with my mouth closed (wow!), but I do still get the vinegary smell in my nose.