If you think it is a software issue then backup your device, put it in DFU mode, connect it to your computer and then restore it and set it up as new via iTunes. Afterwards, check the front camera to see if it works or not. If it does, decide whether or not to restore the backup you just made or continue setting your home screens and installing your apps anew. If it does not work, assume it could be a hardware side and follow the advice given by kch50428.