Divide the nose into 3 parts.
The tip of the nose.
And the outline of the nostrils.
Now, depending on the size of the nose, its shape, and the perspective, draw the rest of the outline.
We will now finalize the drawing.
To begin, refine the curves at the tip of the nose and the around the nostrils.
Now we have a more definite shape for the nose.
Darken the nostrils, which should be the darkest part.
Before making the shadows, imagine where the light comes from.
Here, the source of light is at the top left.
The front of the nose will be bright, whereas the right side and the bottom will be in shadow.
Start by darkening the bottom, while keeping the nostrils the darkest.
Now we'll darken the right side, but slightly less than the bottom.
Always start with the darkest part and do the subtler shading afterwards.
Now, for the finishing touches.
Draw some light shadows on the front to create depth.