Stop talking.
"Button your lip" is an idiom that means to be quiet or stop talking. It is not a figure of speech in the traditional sense, but rather a colloquial expression.
You should talk
You should talk
It means exactly, be quiet, hush, shut up, quit talking.
The phrase button it up means to complete it or finish it.
A lip piercing hurts more than a belly button piercing, but neither hurt much at all. Getting your lip feels like you accidentally bit it haha and you can barely feel a belly button piercing.
up
it means if someones pouting their lower lip sticks out.
I have both my lip and belly button pierced. I had my belly button pierced with a hoop and my lip pierced with a bar/stud. The belly button was more irritating then the lip because a hoop piercing requires the piercer to clamp it shut and fiddle around with a new pierced part instead of just screwing a ball on. I recommend any new piercings to be with a bar/stud as it is quicker and less irritating. Put it this way, I'm going for a 2nd lip piercing and not another belly button piercing ;)
The windows button in the corner or the windows button on your keyboard. Is that what you mean?
It can sometimes mean you have bitten your lip.
Imagine if you had a button on your lip - if you button it, you will keep your mouth closed and be quiet. The same if you hold your tongue between your fingers - it's not moving, so you're quiet. The person wants you to stop talking so much.