iPhone 4 camera problems

iI'm hoping someone can help me with this problem I'm having recently, a few months ago I dropped and cracked my iPhone 4, recently my camera has stopped working. the back camera doesn't work at all but the front camera works sometimes in my camera app and snapchat app, the front camera works all of the time in my Facebook messenger app. I've tried everything to try and fix this problem including reseting and rebooting my iphone, I'm really hoping someone can help me with this problem.