When you enter the PIN number incorrectly 3 times in a row the bank will automatically lock your debit card for security reasons for a period of 24 to 48 hours and then it will automatically be reset.
However you can contact your bank and answer some security questions for the bank and the bank can immediately reset and unlock your debit card so that you don't have to wait 24 to 48 hours to use your debit card.
I've always just called my bank and they've unlocked it within a few minutes after answering the security questions.