There are countless nose shapes. The difficulty is to correctly shade and mold the nasal form.
At first look at the shape of the nose. It is important to distinguish dark and bright areas.
The key to a realistic nose drawing is good shading.
Below there are some nose sketches from different perspectives. The lines are overly hard drawn so you can see them clearly. In a realistic drawing I would form this part only with shading, but not draw sharp lines.
In the sketches on the left and right side, I shaded the side of the nose. The shading lines are adjusted to the form, therefore a lightle arc shaped at the bridge of the nose. I also shaded the form of the nostrils.
Usually the darkest areas are around and below the nasal wings, and on the sides of the nose. Because of the direct light the tip and bridge of the nose have the lightest tone. Nevertheless the shading always depends on the direction of light.
It is much easier to draw a nose from a lateral than a frontal perspective.
From a frontal perspective we see the left and right side of the nose shortened. In the sketch I shaded this area with short lines. The shape of the nose, the nasal tip and nostrils, are mostly done with small curved and round lines.
In the next sketch you can see three different nose types from a lateral perspective.
Nose 1 is almost straight but has a slight concave form.
Nose 2 has a slight bow in the middle.
Nose 3 curves outwards.
To sum up, for me the most important factors art shape, light and the resulting shadows and shading. I "mold" the shape with soft circular strokes. Ever way, drawing noses is a a lot easier when you are practiced in drawing shapes.