The app crashes as soon as I open my world.

I am sorry, but I am not sure what the affects versions are. All of the sudden yesterday, my Minecraft app started crashing. Now every time I try to open up my world, called Gavin's World, the app crashes. I have backed it up on my macbook. I installed the app on my iPhone and installed my backup. But as soon as the I opened the world again, the app crashed. Please help. Thank you.