If you have actually obstructed somebody inadvertently or changed your mind about the block, though, it is likewise reversible. You can alter your Privacy settings to unclog and permit somebody back into your Facebook world.
How Do I 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 desire to unblock. A list of individuals you've obstructed is discovered under the Block Users area.
Suggestion
Unblocking someone does not immediately put that individual back in your good friend list. You need to include the freshly unblocked person as a 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 I Unblock Someone From Facebook with your friends.