Hello Ariel,
You can try installing an extension called Modules Anywhere.
Another approach would be with custom coding. You can create a new module positions and with code in your template block it from appearing in categories.
if( JRequest::getCmd('option') == 'com_k2' && JRequest::getCmd('view') == 'item'):
// something
endif;
This check will only render if it is inside a K2 item.