Tongue in their cheek

This funny-sounding expression indicates that someone just told a joke or isn't being serious! Someone who says something "tongue-in-cheek" is usually kidding.
It's believed that this saying was created by an English humorist in the 1800s. Most people have difficulty saying anything with their tongue in their cheek. But some people actually do stick their tongue against the inside of their cheek after saying a joke to show that they're only kidding.

However when I was young child I was like to joke  to everyone and  now I like to joke with my brothers and sisters.but some people don't like to joke.
Don't joke with someone's feelings maybe you will win the game and perhaps you will lose the person forever.