I have a Lumia 520 that had a small dink on the upper right hand corner with the tiniest crack on it. I was using it like I do normally, and then 5 minutes after I put it in my pocket, a long crack is diagonally across my screen. Bearing in mind this had a case on, I was wondering what caused that crack to grow so big. It's rendered the bottom half of the crack of touchscreen unusable and I don't have the money to repair or replace it. So what should I do?