nexus 4 camera error - can't connect to the camera .

i need a helper to help me out about the bug ... the camera of my nexus stopped working ... i dont know whats the problem with my nexus , main camera dosn't work it gets stuck , but front cam works fine many times ... i formatted the phone many times but no progress , please help me regarding the bug , also tell me if its a bug or hardware or software issue .. leave your comments below ... developers and opinions from you are invited ...