If you're wearing nike clothing for its sporting use - nike shorts to play football, work out, run in. A nike vest to play basketball in, then you're fine. I wouldn't myself (I swear by Adidas for running), but nike make plenty of great running shoes, and some quite fashionable high-tops if you're into that kind of clothing.
Wearing tracksuits as casual wear is pretty chavvy whatever the outfit.
Nobody's going to complain about you wearing a pair of plain black nike jogging trousers to slouch around the house, but not to wear out.