If you have obstructed somebody accidentally or altered your mind about the block, though, it is likewise reversible. You can alter your Personal privacy settings to unblock and allow somebody back into your Facebook world.
How To Unblock Someone From 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 "Unclog" link beside the name of the person you wish to unblock. A list of individuals you've blocked is found under the Block Users section.
Tip
Unblocking somebody does not automatically put that individual back in your friend list. You need to add the freshly unblocked person as a pal and wait for them to validate the request.
And one more thing please don’t forget to share this awesome trick to use the How To Unblock Someone From Facebook with your friends.