What should I do in this situation?
If you think none of the answers are deserving of the bounty you placed, you do not have to award it. In this case, at the present time, Community♦ will not award half of the amount automatically as none of the answers after the bounty was started have got a score of 2 or more.
Can I extend the bounty date
No, however you can start another bounty once the grace period at the end of the current bounty has ended. You will be required to put up at least double the amount you did previously.
should I close the question?
Not if it's a valid question! In addition to this questions with an active bounty can not be closed.
For more information you should see the FAQ on bounties.