Erased and reset watch. Tried to give it away, but says still paired to another account. How to unpair after already erased and reset?

I tried to give my watch to my nephew as a gift. I assumed it was unpaired because it didn't show up in the apple watch app on my iphone. So I erased/reset it and gave it to him. he tried to pair it to his phone, but it still says it's still paired to another account (mine). How can I unpair it now that I already erased the data and it already appears to be unpaired on my end?