Hello and welcome to Android Forums. Hopefully I can help you with your problem.
I would try several other camera apps from the Play store and see if that helps. If those cameras work then you probably have issues with the app itself. Make sure you've got all of your pictures backuped up to a computer. Most cameras save to the sd card but not all. Then go into your phone settings/ applications and locate you camera app. Select the wipe data option and then reboot. If you still cannot access your front camera then you may have hardware issues.
My next step would be to do a factory reset. Make sure that you backup all of your phone and app data 1st before doing so.
If your camera still isn't working, I would check the warranty status. If it's still under warranty you may have to ship it back to the manufacturer.
If you have any other questions regarding your device, I invite you to join Android Forums. We have many sections for specific devices which contain a wealth of information.
