Has it always been black or is it a new thing for your cat?
If your cat usually has a pink nose, which now has black flakey scab-like bits, it could be skin cancer caused by sun damage. White cats and other coloured cats who have white fur on their faces, often have pink noses and are more susceptible to skin cancer on their nose. It can be treated if caught early enough, by a vet, usually by surgically removing the affected spots.
If your cat doesnt have a pink nose, the black on his/her nose is more than likely, just pigmentation on the nose, which can either be black or brown.
If your cat usually has a pink nose, which now has black flakey scab-like bits, it could be skin cancer caused by sun damage. White cats and other coloured cats who have white fur on their faces, often have pink noses and are more susceptible to skin cancer on their nose. It can be treated if caught early enough, by a vet, usually by surgically removing the affected spots.
If your cat doesnt have a pink nose, the black on his/her nose is more than likely, just pigmentation on the nose, which can either be black or brown.