It's a nicer way of saying ''I don't care''
Example 1 :
Sasha : I Have This New Amazzingg Boyfriend
Emily: Nice To Know.

Example 2:

Elli: Today Is A Great Day For Me, I'm Having The Best Luck I've Ever Had
Brandy: Nice To Know.

Example 3 & Last One :

Jordan: I Love Her SOO Much.
Caitlyn: Nice To Know. I Wish You Guys The Best.
by Kayla Crowder August 20, 2013
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An expression said to someone who is about to do something which will put him/her at great risk.
Mark: "Hey man, did you sell your plasma screen TV yet?"
Johnny: "Yeah, I've got a guy who wants to buy it. I'm meeting him on a corner in East Oakland tomorrow night at 1am."
Mark: "Good luck with that. Nice knowing you."
by Nicholas D January 13, 2012
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