cutline theme, header error blocking my log in?

I modified my cutline theme header to put in an image and probably made some error cuz I’m a newbie at wordpress and computer stuff generally. The image looked fine but if I tried to publish a post I’d get a header error message like I now get when I try to log in (see below). I didn’t care much about this problem before cuz if I just hit “back” and then went to my site the post would be published.

I think I didn’t have trouble accessing my dashboard before because I had an “admin” link on my blog that worked fine. But now the “admin” link has disappeared (maybe a cookie got deleted?) and if I use the log-in link I get this message:

Warning: Cannot modify header information – headers already sent by (output started at /home/markzima/public_html/wp-content/plugins/batch-categories/batch-access.php:11) in /home/markzima/public_html/wp-login.php on line 9

Warning: Cannot modify header information – headers already sent by (output started at /home/markzima/public_html/wp-content/plugins/batch-categories/batch-access.php:11) in /home/markzima/public_html/wp-includes/pluggable-functions.php on line 309

Warning: Cannot modify header information – headers already sent by (output started at /home/markzima/public_html/wp-content/plugins/batch-categories/batch-access.php:11) in /home/markzima/public_html/wp-includes/pluggable-functions.php on line 310

Warning: Cannot modify header information – headers already sent by (output started at /home/markzima/public_html/wp-content/plugins/batch-categories/batch-access.php:11) in /home/markzima/public_html/wp-includes/pluggable-functions.php on line 272

The “cannot modify header inormation” message resembles what I’d get when I published posts previously.

How can I access my dashboard now?

My Filezilla can still get in, is that of any use?