You can use the mail recovering method only if you have an active Internet connection. If not, in order to unlock your phone, your only choice is to do a factory reset. This will wipe all your data from the device, but you will be able to use it again. To do a factory reset, you first need to turn OFF your phone. After you did that, press and hold the Power button together with the Volume Up button until the Android logo appears on the screen. This means that you entered the recovery menu. Use the Volume buttons to navigate through it and select the Wipe data / Factory reset option using the Power button. After your device is rebooted, the password should be removed and you will be able to use your device again.