No you should not unpublish your book if you need to edit any text, the cover or interior. This could mean waiting longer than necessary for it to be approved again, as well, it will not be available on Amazon.
Just make your edit to your book by finding your book on the KDP Bookshelf, mouse over the ... on the right side of it, and pick one of the 3 edit choices. Once done, click save and publish on step 3.
You original book will stay for sale on Amazon while KDP looks to approve your edits, once they have, your updated version will be available to people on Amazon.