Its not unusual this time of year in the NE to find a hive with a mother and daughter queen, the daughter may start laying soon. I would just leave the nuc alone and not disrupt your hive by adding the nuc. This late in the year you don't want to take the chance that you could be adding mites, diseases, or sick bees to your healthy hive. I know its recommended to cut your losses in the fall by combining failing hives, but I never do. My hives are all dialed in by mid to late September, young queens, stores, low mite counts. I don't want to add any issues or stressors with all of todays pests and diseases.
The worst that can happen is the nuc will fail and you'll have drawn frames to start a new nuc in the spring.