Turn your phone off.
Press and hold the Power/Lock Key and both of the Volume Keys (on the back of the phone) at the same time for more than 6 seconds to enter Hardware key control mode.
Press the Volume Keys to scroll to Mode ON, Mode OFF, or Cancel, then press the Power/Lock Key to confirm.
If you use your phone with a broken display glass, your phone may incur additional damage or cause injury. Make sure to visit an LG authorized service center to get your phone repaired.