Big Brother Final 4 Power of Veto Rules?

In Big Brother, let say there are 4 house guests left (player A, B, C, D). If player A won HoH, player B&C got nominated. Then after PoV competition, player D won PoV. If let say player D uses PoV on player B, who will be the replacement nominee? Since player D is the winner of PoV, so player D cannot be nominated right? So there are no house guests left to be the replacement nominee.