Look at the image showing the structure of the nose. Feel with your own nose whether my explanation is correct.
Left: The nose starts between your eyebrows with a hard bone. The bone is drawn very straight for convenience.
Middle: At the bottom of the bone your nose becomes soft, drawn in the middle as a ball. That is ‘the tip of your nose’.
Right: The nostrils have now been added. A little shadow makes the nose a bit rounder. The light side of the ball has been erased.
Exercise 1: Draw a nose in the three steps next to each other as in the image above.
Exercise 2: now draw the nose with visible nostrils as in the next example
With a nose from the side, straight assisting lines are useful. Here a upturned nose and a crooked nose, with and without the (red) assisting lines.
Exercise 3: Draw a crooked nose and an an upturned nose from the side.
Exercise 4: Try a nose half sideways (in three-quarters) as below. Clearly show that the nose has a front. That front side is often forgotten. You can lighten those lines later. The shadow lines (hatching) nicely follow the shape/roundness of the nose.
Extra: there are many beautiful, strange and funny ways to draw noses. How many different types of noses can you draw? Maybe you’d like to draw some of the following noses below or make noses up yourself. You can add up heads and bodies if you like.
Especially in comics and cartoons you’ll come across special noses. For example Big Nose from Pink Panther has a huge nose and Pinocchio gets a long nose when he tells a lie.