To reset all local changes, delete the contents of your project’s /Saved/Config/ directory.
If you changed the default settings of your project, however, then things get more complicated, because that will modify the Default INI files in the project’s /Config/ directory, and we currently do not have a mechanism to reset those to the project template defaults (this is something we’re working on right now).
If you remember which project template your project was created from, then you can delete the contents of your project’s /Config/ directory and overwrite it with the contents of the /UE4/Templates/TemplateName/Config/ directory.