How to Unblock Someone on Twitter
When someone is annoying you on Twitter, you have the option to unfollow them or to block them. Blocking someone on Twitter automatically forces their account to unfollow you, and blocks them from following you again. It also stops their tweets from appearing in your Twitter timeline. It does not stop them from visiting your profile page, unless you have a protected, or private, account. Twitter does not notify people that they have been blocked, however they may suspect you blocked them and unblocked them if they notice they are no longer following you.
Open a web browser and log into Twitter with your username and password.
Type the person's name or username into the Twitter search field. Hit "Enter" on your keyboard.
Click the "People" tab.
Browse the list of accounts to find the person you blocked.
Click the name of the person you blocked. Their profile will appear on the right side of the window. Where the "Follow" button normally is, you will see a box with a line through it with the word "blocked" beside it.
Click "Undo" next to the word "Blocked."