There is no scientific reason behind nose piercing. Nose piercing is a fashion statement and has no great benefits. Nose piercing does not add or subtract any substantial thing to your body.

Piercing has lot to do with identity than science. Piercing and body modification is not a new thing. People are doing it since ancient times.

Tribal people in ancient time used body piercing to identify their clan, to make their clan look different from other clans.

It was a means to identify ones clan member and to protect it. But as time passed it became a kind of fashion statement than clan statement.

Nose piercing has nothing to do with modern science but ancient science suggests that piercing nose near marma (a particular node)  helps a girl somehow during menstrual cycle and child birth.