Well, I don't know any direct way but...
There's a little triangle with a red border next to each post that is for reporting bad posts. Whilst you can't actually report your own posts, you can either press this next to the first post in your thread that you want deleted and explain it in the blank box that comes up after or get one of us to press it on your original post. This will get the mods attention and they'll be able to do something about it - hopefully delete it.
Alternatively, you could edit your post and ditch anything you don't want in there. Of course, this won't get rid of the thread though.