I'm arriving into NBO on a QR flight in J that arrives at 11:55pm and want to book a KQ flight to ZNZ that departs at 8:00am. Rather than get a hotel, I'm inclined to spend the night in one of the KQ lounges. Do I need to book my NBO-ZNZ flight in J in order to access the lounge, or can I purchase a pass to the lounge?

I just realized there are Priority Pass lounges at NBO. Presumably that's a better option. Am I correct?