Quickly, before I run out, this is not something that should be very difficult to break. It's just a matter of limits. Nipping is very different than biting and dogs at that age will try to test limits. Really, he's just trying to play and needs to be taught that it is NOT ok to play like that.
Our rescue Winston came to us this summer at around the same age as your Winston and he tested w/some nipping when excited and wanting to play...
Here is what we did:
1 - Kept him on a prong collar with a leash or a tab when in situations that he might nip. Our problems came in the backyard with our kids (aged two and four) so I just always had him on a leash and prong for a while (several weeks, and then as needed .... still do it intially when in the backyard when Winston has "beans"). That way you can correct.
2 - We gave Winston an opportunity to nip and wrestle that WAS OK.... for us, it's the daily dog park, where dogs can wrestle and bite and chase... we do that EVERy day. or most every day. You could set up play dates for your boy. Give him the space where that is OK (but ONly with other dogs ... do NOT let him do that with people,e ven adults).
3- We tired Winston out each day, we also, as he was adjusting, notonly did the dog park but did MASSIVE hikes/walks each day. At sixteen months, your boy is at his PEAK energy levels, and just needs to drain a bit...
4- we did a lot of distraction from bad behavior w/treats because our W. is treat motivated
5- Finally, for us, as suggested by the wise minds here, we used "ignoring" behavior. That is the MOST effective. When Winston gets rough, we just all leave immediately and he is totally alone in the backyard. A few minutes later ... the crying begins. He has learned, if I chase/nip the people, I get left alone. To a newf, that is the worst thing that can possibly happen.
We don't scold or chase or yell when Winston does bad behavior. I keep totally silent. Any of the above will further excite him as it mimics play behavior.
Good luck... hope others chime in, there is so much good advice here.
Liz