When someone you know begins to ignore you. Specifically if someone ignores you because they have recently gotten into a relationship. If a friend of yours gets into a relationship and suddenly begins to ignore you more, chances are they're pulling a nicky.
Once they get into a relationship, they will likely not want to spend time with you and refuse your requests to meet up and instead spend all of their time with their partner.
Person 1: have you seen John lately?
Person 2: nope, haven't seen him. He's recently got himself a girlfriend though.
Person 1: oh no! He's not pulling a Nicky is he!?