Front Screen preparing

My screen broke down but the screen protector didn’t break i don’t know the reason but I bought my iPhone 4 months ago so it’s still in warranty & i can’t prepare it by a huge price because it’s not my fault, yes it dropped but from very low hight and on a grass “a very soft land” and the fall can’t broke it so i think it’s not a usage defect. So, i want to know what I should do?