If you would like to delete a blog from your account, use the Blogs menu at the top of any page to navigate to the blog. From there, go to the Settings page. You will then be on the Basics page, where you can delete the blog using the Delete this blog link at the bottom right.
After clicking the Delete link, a pop-up confirmation will open where you will need to confirm the removal of the blog. Click OK and the blog will be deleted.
Please use caution when deleting a blog as all the content of the blog, including any files uploaded to the blog's folder, will be removed.
Instead of deleting the blog, you may want to consider enabling password protection. By password protecting your blog, the blog will be kept in your blog account but no one will be able to view the blog without signing in.