you can delete your course after it is published. Here is how to delete your course,
Login as admin and in admin dashboard go to Courses > courses tab > select a course
In course builder go to Settings > Advanced Settings > Delete This Course and click on delete. On confirmation this will delete your course.
Note: But you might want to make sure that there are no students enrolled to the course. Also, if the course is published one then you first need to un-publish to delete it.