Question

What might happen if the pupil of your eye could not change size

Answer 1

that is not possible/likely. you don’t realize when your pupil changes size. if your pupil does not change size/dilate in the dark, then you would not be able to see.

Answer 2

your retina could be burned because the pupil won't be able to become smaller and keep excessive amount of light from coming in as the pupil regulates the amount of light coming in