You can delete your thread with the poll if no one else, including you have posted a reply on that thread. Otherwise you can only lock that thread and wait until that thread disappears behind the last pages of the section and/or moved to the archives section.
If you dont know what you are talking about dont speak
OP, in many sections of the forum, you can delete your thread with the poll if no-one has seen the thread yet, but you cant just erase the poll, just copy the text and start a new thread without the poll, you can also try moving the old thread to archive