If you unblock someone and immediately regret it, you cannot instantly re-block them. before you can block the same person again. This rule prevents users from abusing the feature to harass others. Do They Know You Unblocked Them?
without appearing in "People You May Know" Restrict their access to your posts if you'd rather not. Let me know which direction you're heading. Unblock a Facebook profile, Page, or nickname what happens when you unblock someone from facebook