how to remove a blog from list of "my blogs" in wordpress dashboard?

I need to remove a self-hosted wordpress blog (ofsmallthings.org) from the list of my blogs that show up when I sign in at wordpress.com. The blog is no longer mine and I cannot sign in to its dashboard, but it is auto-posting to my twitter account, and I believe this is being done through jetpack’s connection with wordpress.com. What do I have to do or who do I have to talk to so that this gets undone?