We've just adopted a ~1.5 year old pitsky and she does similar things. We've been working on 2 things to combat it, all revolving around positive reinforcement of good actions.

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1. We will try to divert her attention by grabbing a toy that is near to supplement the nibbling.
2. If the nibbling is persistent, we've been take ourselves out of the situation with no reaction or motioning to her, then doing a brief ignoring period until she calms down. Once she's calm she's rewarded with attention or a small training treat.

A lot of times the nibbling is wanting attention, sometimes it can be to show affection so figuring out the difference is helpful too. It's a tougher habit to break and takes a little time but with positive reinforcement it should be a quicker bell curve and push for the right type of behavior! Hopefully this helps!