If you have actually blocked somebody accidentally or altered your mind about the block, though, it is also reversible. You can change your Personal privacy settings to unblock and allow somebody back into your Facebook world.
How Do U Unblock Someone From Facebook
1. Click the down arrow beside "Account" on top right of any page on Facebook.
2. Click "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 "Unblock" link next to the name of the individual you wish to unblock. A list of the people you have actually obstructed is discovered under the Block Users area.
Idea
Uncloging somebody does not automatically put that individual back in your buddy list. You should include the recently unblocked person as a good friend and await them to confirm the demand.
And one more thing please don’t forget to share this awesome trick to use the How Do U Unblock Someone From Facebook with your friends.