Yes, technically you can rule-lawyer past the restriction, but you are just spoiling the point of the monster by doing so.
Its like having someone hit a flaming monster and taking damage and therefore the monster is no longer flaming it for the second person who hits it in the same 6 second span of time. Whether that's what the rules technically allow or not, it is against spirit of what is meant to be relayed by the rules.
To get rid of the Nilbog, obviously you heal it to death. But I think they aren't supposed to try to hurt you anyway, they are just supposed to be annoying.