I won the key, but its not legit...Steam says the key is "already used on another steam account"

I bought the key today in a bundle and i already had the game :/

well i dont really care too much about getting it, just wont press "recieved" when key was used.
Not sure, if you can delete this giveaway after finish.. if so - just delete it.
If not possible, well... maybe contact bundle sellers about used key in bundle? Maybe they just will send another..