Our girls like to do more than just nibble-they chew,scrape or whatever you want to call it. Especially my husbands ears.
We got them together from the same breeder at the same time, and he told us they were 6 weeks OOP. We didn't know at the time that was really too young.
So I speculate that one (Cheyenne) is a little bit older than the other, Luna. Cheyenne likes to chew the back of my husbands ears, where the cartilage is. It makes quite a crunch.He can get her to stop by pulling his ear out of her reach by turning his head. But Luna likes to chew the tops of his ears, and take a big chunk out (scrape some skin off). Its harder to get her to stop.
People have suggested he wear headphones, distract them with a treat or a toy, take them out in a less familiar environment: we take them out in a glider-proofed bathroom. We have used the living room and they don't bite out there, but it makes me quite nervous.
They like to chew on me if I wear short sleeves, but that isn't a problem right now since it is getting colder. Supposedly you can imitate a mother glider and go "ch-ch", but it only sometimes works for my husband. Blowing on them sometimes works when they are chewing on my arm, but I don't really like to do it because they say not to do it if they can see you. I sometimes kiss them while they do it, and that works in certain locations on my arm. One thing that seems to work pretty well for me is to put my finger on her nose, she picks up and tries somewhere else, and I put my finger on her nose again. She doesn't like it so she stops.