Hey Roshan,

I am really sorry for the delay of this reply as it is a weekend for us here. This cannot be configured currently but you could try running the following SQL query to hide the "Registered" option in the privacy under the story form,

[gist]
update jos_social_privacy set options = '{"options":["public","friend","only_me","custom"]}' where `type`='story' and `rule`='view';
[/gist]