Why does my parakeet "nibble" on my fingers?

Question

I finger trained my parakeet very well but it is starting to open it's beak and swish it's tongue back and forth on my finger.

Answer 1

It sounds like your bird is trying to preen your finger.  That means it likes you; birds in a flock will preen their friends.

Answer 2

The parakeet is grooming and bonding with you.

Answer 3

  It's how they feel things. He's trying to get to know you better.