if your site collection admin than its simple!
http://YouRootUrl/YourSubsiteName/_layouts/user.aspx and now select Inherit Permissions within the ribbon, that should reset the site back to normal!
central admin -> under site collection click on 'change site collection admin' -> within the drop down box for site collection you can select the site, on the right side it will show you the site on the left the subsite, select the subsite in question and click ok. now add your user account name and click ok! you should be able to login to the subsite as normal!
lol just noticed the deletion part ;) atleast the above is to give you control to the subsite again without having to delete the subsite :)
you could use stsadm aswell!
stsadm -o deleteweb -url http://server_name/sites/site_name/subsite_name -force
i know stsadm is for 2007 but it works in 2010 ;)