Yes, good catch tribephyl! And I agree with your analysis michel!Note: Around camp both Vince and Nina wear a "ring" on their ring finger (i.e. left hand)
Nina's looks like a silver colored wedding band
Vince's looks like Black string tied around his finger?
Looking at the first Immunity Challenge it appears that Vince takes off that Black Ring (Note: This is easier to see watching the video)
However, Nina wears her wedding ring during the first Immunity Challenge
So assuming Vince would take off that Black "ring" and Nina would wear her silver wedding band in a subsequent challenge...
I think that is Vince's Left Hand with the Black Ring removed. I don't see a silver wedding band and it doesn't look like a woman's hand that is shorter than Hali.