Sometimes I REALLY wish this board had a FAQ.
You can call AirBnB and plead your case to see if they will remove the block. If they do not remove the block those dates will remain unavailable for booking through AirBnB.
If the person you agreed to let stay did not use AirBnB to find your listing, ie: they are a friend or someone who responded to an ad that you ran outside of AirBnB, AFAIK there is nothing in AirBnB's TOS that would prevent you from renting to the person directly, or through another platform.