If you have actually obstructed somebody inadvertently or altered your mind about the block, however, it is likewise reversible. You can change your Privacy settings to unblock and permit someone back into your Facebook world.
How Do U Unblock Someone On Facebook
1. Click the down arrow next to "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 "Unblock" link next to the name of the individual you wish to unblock. A list of individuals you've blocked is discovered under the Block Users section.
Tip
Unblocking somebody does not instantly put that individual back in your buddy list. You should add the recently unblocked person as a friend and wait on them to validate the request.
And one more thing please don’t forget to share this awesome trick to use the How Do U Unblock Someone On Facebook with your friends.