One bite of an apple is an example of a nibble.
A phone call back about a business plan you've been proposing is an example of a nibble.
When you take just a few small bites of cheese, this is an example of when you nibble.
When you grab a piece of an apple, then a few cookies as a snack between meals, this is an example of a nibble.
When you constantly find reasons to prove points in an argument, this is an example of how to nibble away at an opponent's argument.
Fish nibbling at the bait.
Nibble a cracker.
He nibbled at my neck and made me shiver.