Well this is annoying...

What game?

The giveaway creator can't delete the giveaway now, but I think you can. Go to the GA and see if there is a delete option on the lower right (I believe). But I'm not sure if that's the correct way to handle this.

I accidently gave away a trash game that was region locked, and was won by a guy in china. we agreed to delete GA. Msg'd support. 3 weeks later it got deleted. Poor guy, I felt for him.

From FAQ:

What should I do If I win a game that cannot be activated in my region, or if I receive a gift or key that does not match the game I won?
You should contact the giveaway creator to return the gift, and to inform them of the situation. If the giveaway creator is able to provide you with a replacement gift or key for the same game that can be activated in your region, then you should mark the gift as "Received". In all other cases, the gift should be marked as "Not Received". When marking a gift as "Not Received" it's recommended that you leave an explanation in the giveaway comments as a reference for both the giveaway creator and our support team. If the giveaway creator is not able to provide a replacement gift or key, they may ask your permission to delete the giveaway.

This is one of those situations in which a modification to benefit users can cause a problem in very specific cases. In this case, I think not allowing GA to enter previously earned is good and beneficial. I'm sorry that you have fallen into that limbo of not being able to redeem the game and not be able to enter new GAs of that game at the same time. Your only hope is to be patient and wait.

He has been online on steam, but hasn't allowed me as a friend...
but hasn't been back here yet.
If he comes back here and does nothing i will do a support ticket maybe..