If you have obstructed somebody unintentionally or changed your mind about the block, though, it is also reversible. You can alter your Personal privacy settings to unblock and enable somebody back into your Facebook world.
How Do You Unblock Someone On Facebook
1. Click the down arrow beside "Account" on top right of any page on Facebook.
2. Click "Personal Privacy Preferences" from the Account menu.
3. Click the "Edit Your Lists" link under the Block Lists heading. It is at the bottom center of the page.
4. Click the "Unclog" link beside the name of the person you wish to unclog. A list of individuals you have actually obstructed is discovered under the Block Users area.
Pointer
Uncloging somebody does not automatically put that individual back in your pal list. You need to include the recently unblocked individual as a good friend and wait on them to confirm the request.
And one more thing please don’t forget to share this awesome trick to use the How Do You Unblock Someone On Facebook with your friends.