Ok so color of nose has nothing to do with the dogs breed. It only has to do with the color of the dogs nose. Usually a dogs nose will be a similar color to the color of the dogs coat, like with blue dogs you usually get a blue nose or a black nose, and with red dogs you usually get a red nose, black nose, and with dogs that have white on their face to the nose, the nose can be pink. So a chocolate pit bull might have a brown nose, there is nothing rare about it, and don't be pulled into the nose color hype, they are all dogs.
A brown nose pit comes from a red nose pit and blue pit mix, they are uncommon due to there are not many litters that will throw a brown nose pit. I have a red on red brindle brown nose pit that came from my blue/ american pit and a friends blue/ red nose. I have been looking for another brown nose to breed her with and its been hard to find one.
I've never heard of a brown nose pitbull, I have only heard of blue nose and red nose ( which is actually a black nose or red nose pitbull).