Hi there and welcome
Is it a sort of crust?
When my eldest girl, Emily, moved in 15 years ago after a feral life, I noticed a caked black discharge from both nostrils, one worse than the other.
I assumed this was the result of what's called a low-grade infection, which may be brought on by stress (she'd recently been neutered and even a move from streetlife to a safe home is an upheaval - oh, and there'd been kittens as well.)
I reckoned the vets ought to have spotted anything untoward and since she was thriving otherwise, I just kept my eye on it, I'd gently scrape it away when she'd let me ... oh happy days, picking a cat's nose ...
It went away by itself in time and she's now a healthy old lady of almost 16
BUT if you see any more sinister symptoms, such as not eating, miserable, crusted eyes, sneezing a lot or nasal discharge, please do get your cat checked out. There is a nasty called calicivirus which I believe is a form of flu, which may need more specialised treatment. But I hope this isn't the case!
And hopefully there will be others along soon with more info and advice, but hope this helps for now, please let us know how the cat gets on, all the best.
