* Buenas noches: This is Spanish for "good night."
* Nachos: This is an English word referring to a popular Mexican dish.
* Gracias: This is Spanish for "thank you."
Putting them together doesn't create a coherent phrase.
It's likely a playful way of saying "good night" and expressing thanks.
It could be used in a situation where someone is offering nachos, or it could be said jokingly as a lighthearted way to end a conversation.