I am inexperienced as well so take this with a grain of salt and maybe someone with more experience can comment about this.
When I initially read it I was thinking that instead of nicking him on the sit, I would nick him on the here when you call him back. Seems like that would eliminate the dog wanting to leave your side prematurely.
Like I said just a thought. Have at it everyone.
thanks for the replies to this post. They make sense.