A lot of Blogger/Blogspot users are always looking for way how they can imitate the “Incoming Search Terms” plugin of WordPress. The said plugin is a great help for the SEO of a blog and it was greatly enjoyed by WP users.
I have done a search before if an “Incoming Search Terms Plugin/Widget” for Blogspot exist. I even wrote about it on an article here. During that time (January 2012), no plugins like that or close to it exist.
Take note that “it will take time before the content of this widget appear”. Just be patient waiting for it as it gathers backlinks. Enjoy!