Paginated PAGES are getting Indexed by Google.

I have been getting problems with the paginated PAGES (not posts). Recently I wrote a long article which I wanted to split in various pages.

I used the following code to split the pages and it worked:

<!--nextpage-->
more
<!--nextpage-->
more
<!--nextpage-->
more

Got the desired result but the thing is that the paginated pages are getting indexed also which I don’t want.

I used this code in my page.php to show the pagination

<?php if ( function_exists('wp_pagenavi') ): ?>
   <?php wp_pagenavi( array( 'type' => 'multipart' ) ); ?>
<?php else: ?>
   <?php wp_link_pages(array('before'=>'<div class="post-pages">'.__('Pages:','hueman'),'after'=>'</div>')); ?>
<?php endif; ?>

An article from Google regarding the paginated posts (https://webmasters.googleblog.com/2011/09/pagination-with-relnext-and-relprev.html)

See how it looks (my test paginated page) – https://prntscr.com/bsqsvp

I just want to index the main page excluding the sub pages. Hope my problem will be solved soon.

Thanks