: If you unblock someone and then change your mind, Facebook requires you to wait 48 hours before you can block that same person again.
The mobile app interface places the "Blocking" menu within the section.
As mentioned earlier, unblocking is not the same as re-friending. Once you unblock someone, you are essentially just "strangers" on the platform again (unless your profile is public).
Note: If you had previously unfriended them but not blocked them, they might still be on your friends list. However, usually, blocking someone automatically removes them from your friends list, meaning you have to re-add them.