Personally, I don't like it. A "nub" is a small piece of something, often left after the rest is worn away. A pencil can be "worn down to a nub." I don't think that's the feeling you want to give with a cosmetic brand, especially one related to nails. Women do not want fingernails that are nubs.

No. When you draw back a nub it means that you've cut your finger off.

It does not really work in English - the juxtaposition of nail and urban sounds odd and NUB as a an acronym sounds very dull.