I've been away from BPO for awhile, so first, welcome!
Cassie was a big "nipper" when we first adopted her, so I relate. It wasn't an aggressive thing with her either, just something she did when she was trying to get our attention or was feeling super playful, but very annoying & sometimes painful. When she'd do it, we'd say "no, mouth!" and then hold our hands near our chest and immediately turn our back on her. I didn't want to use the term "bite" b/c I was afraid that others would get the idea that she was doing it aggressively. We'd keep our backs turned to her for from a few seconds up to 1/2 minute or so, or until she settled down. Once she'd sit or stand still and look puzzled ("why aren't you playing with me, Mom?"), we'd turn back to her and praise her quietly and give her a pet or treats. We did the same thing if she jumped on us (except we said "no jump!").
I was very happy with this method b/c it was totally gentle (very important to me!) and she learned very quickly! Within a week or two she was quite reliable. From then on she has seldom nipped or jumped, but when she does, we just handle it the same way and then she remembers.