Help…can’t access my admin anymore

Warning: Cannot modify header information – headers already sent by (output started at /home/content/m/y/e/myersjj6/html/wp-content/plugins/twitter-follow-me-box/tfmb.php:13) in /home/content/m/y/e/myersjj6/html/wp-includes/pluggable.php on line 868

When I try to go to admin in my blog I get the above message both where the admin bar usually is and when I attempt to go there directly via url.

Can someone help me figure out how to get back in so I can correct the error? Help much appreciated