File a support request through the hel p page explaining the situation. Make to sure to include hour old user-name as well as the email address it is registered to and support should be able to get you straightened out pretty quickly.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .