One other possibility — though rare — is a fungal sinus infection. Or for that matter a regular bacterial one. I’ve been dealing with a fungal sinus infection for almost two years (just recently diagnosed), and in the beginning I had the most vile smell in my nose. I hate to even say it, but it smelled like dog poop. This happened in the months after sinus surgery, so it’s also possible it was scabbing in my nose from that. Good luck! I know just how gross this can be 🤢.