Truffles likes to pull at fluff on my dressing gown. She tried this on my arm, and 'pinged' my skin three times, these came up in tiny raised bumps. She didn't break the skin though. I think she'll always be inclined to nibble, it's in her nature. I don't love her any less for it, and just remember to not let her near my skin, although she does lick my hand from time to time.
BonBon had me once at bath time, she didn't like it (first water experience) and meaningfully grabbed at my wrist, drawing blood. Although they are flight animals, they will sometimes bite to defend themselves if cornered, that's why they also chatter their teeth as a warning... especially from water

Truffles chatters her teeth at my husband when he goes to pick her up from floor time, but she's yet to take it any further, not to say she won't. She's a spritely character, knows what she wants, always the loudest at feeding time, yet also the most sweet at lap time, she's more than happy to sleep in my arms, or snuggle up on her favourite pillow (yes, she has her own fluffy pillow

).
I would have thought Tilly would have been the most likely to nip, as she has a timid nature, but she'd rather run and hide first, and has never chattered her teeth. She's just learned to lick, and is becoming a lap pig, but will probably take a lot longer to.