This has been in the master branch of Nikola for a while but only now have I tried to fully integrate it, and polish all (most) of the rough edges.
By default, Nikola comes with support for search forms using Google and Duckduckgo. Some people disapprove of them for different reasons  so there was a request about supporting a standalone search engine.
The best of breed of those things seems to be Tipue so that's what I supported.
To use this, you need to enable a plugin, and do some configuration changes.
The plugin is called
task_localsearch and you can find it in
the Nikola source tree
Suppose your site is in a folder called
mysite then to enable this plugin you need
mysite/plugins and then copy
Then, in your site's
conf.py find these options and change them accordingly:
How does it work? Here's a demo site for you to try!