From above - if the item has met the reserve you set, then you cannot retract the item and sell it to someone else on a buy it now basis. The best thing for you to do is to inform the person that you made the offer to that you have now had a bid on the item, but that if it does not reach your reserve (assuming that you have set one) or that the winning bidder does not complete the purchase, then you will consider selling it to them for their original offer price. Once you have had a bid on an item that meets your reserve you are bound by e-bay regulations to honour the sale to the winning bidder, as long as they pay up!