By mistake added phone lock from "App corner" in setting. Now there is no option to revert it back. I am using Nokia Lumia 620 with windows 8.1
In case, you are not able to remove the phone lock, the last way is to reset your phone.
Before you proceed with the steps, make sure your Windows Phone is enough charged. As a precaution, charge it for another half an hour before you try this.
Now, disconnect the charger and switch off the phone. I said to remove the charging, since your phone will automatically turn on if you try to switch off while in charging.
Once you Windows Phone is switched off, press volume down and camera button at the same time. Also, hold the the power key at the same time.
Your Phone will vibrate. Release the power key but keep on pressing the volume down and camera button until the phone reboots. Your phone will reboot to its factory settings and all the data will be erased from your phone. So, basically you will have the phone in the same condition in which you bought it from the store. No more password.