I can't turn the light off in my aquarium. What should I do?

I have Fluval Chi aquarium with one goldfish in it. The LED lights won't turn off anymore. The crappy design means that I can't unplug the lights without turning the filter off. I can't return the aquarium until tomorrow, and I left the lights on all night last night. The water is still cycling and my nitrate and nirtite levels are still high. Should I use an old filter I have overnight so that I can unplug the lights, or is it better to leave the lights on?