It can only be done if you select pin as your lock screen. To do so, you have to go to Settings -> Security and Privacy -> Lock Screen -> Screen Lock -> PIN and while setting Pin, tap on "Confirm PIN without tapping OK".
It can be done if your pin is Of 6 Digits...To do Follow the steps:- Settings -> Security and Privacy -> Lock Screen -> Screen Lock ->Then Tap on Confirm Pin without Tapping OK
As per your concern, we want to inform you that if you set the PIN as device lock then you will not get the OK option while unlocking the device. Follow the given steps to set the PIN on your device.
