Help pokemon Y mysterious egg!!!!

So i got pokebank to get a celebi and transfer some pokemons to reset my game went I use pokelink it say that something was in my transfer box I went to pokebank and in the transfer box there was an egg I take the egg and try to hatch it but then I realize that it was a mysterious egg and every time i o to pokebank there is one in the transfer box what can I do please help. Thanks