You are very observant, it’s one of the least things I thought anyone would figure out, in my honest opinion this work isn’t perfect or a finished work there are still work to be done and the pupil is one of those and I wish I spent time on.

I have a little sketch here

If you observe the human pupil, you will notice it has a little protrusion, especially when you are looking sideways, but in my drawing mine looked like a sphere or like it facing the viewer directly, that’s why it looked flat in the eyes, and I didn’t pay much attention to lighting and tonal values like the dark areas and my highlights, so it’s not the camera it my hand and I wasn’t focus at that stage, but I decided to share anyways.

Here is another sample

But be very careful when, trying to make a curve around that area so it doesn’t look too curvy.

https://www.shutterstock.com/search/eye-side-view