A few tips on drawing Anime noses and how to do the shadow. ( in my style)
Noses can be difficult to shade if your not familiar with the shape. The shadow will be different according the the type of nose you are drawing. The noses i have drawn have a bridge that extents up all the way to between the eyes, and the shadow is done accordingly.
If there is less of a bridge there will be less of a shadow on the upper part of the nose.
The nostrils aren't always shadowed, especially if there is more than one light source or the light is coming directly from the side of the nose.
The shape is pretty straight forward, but the problems come when trying to draw it from different angles, once again i suggest a mirror or to look at some reference pictures, even if there from real life since its easy to convert itto manga
Hope this was helpful