wp-admin not working

I recently updated my wordpress version and recently added the twitter plug-in (the last time I logged in) tonight I try to log-in to my https://domain.com/wp-admin and I get the following message:

Warning: Cannot modify header information – headers already sent by (output started at /home/hogfarme/public_html/wp-content/plugins/twitter/widget_twitter_vjck.php:171) in /home/hogfarme/public_html/wp-includes/pluggable.php on line 896

I can not go to any of my pages, even /wp-admin/edit.php shows the same message.

How do I fix this?