<?php
       $prev_post = get_previous_post();
       $next_post = get_next_post();
       ?>

       <nav class="post-nav section">
        <div class="row no-margin">
        <?php // Display the thumbnail of the previous post ?>
        <div class="col-xs-12 col-sm-6 prev-post" style="padding:0px">
           <?php
         $prevPost = get_previous_post();
            $prevthumbnail = get_the_post_thumbnail($prevPost->ID);
            $post_tile=get_the_title($prevPost->ID);
            $thumb = wp_get_attachment_image_src(
              get_post_thumbnail_id($prevPost->ID), 'full' );
            ?>

            <div class="post-nav-thumb" style="background-image:
             url('<?php echo $thumb['0'];?>')" ></div>
            <div class="post-nav-content">
            <div class="post-nav-subtitle"><?php
            previous_post_link('%link', 'Prev Post'); ?></div>
            <h2 class="post-nav-title"><span><?php
            previous_post_link('%link', $post_tile); ?></span></h2>
            </div>

        </div>

    <?php // Display the thumbnail of the next post ?>
        <div class="col-xs-12 col-sm-6 next-post" style="padding:0px">
          <?php
            $nextPost = get_next_post();
            $nextthumbnail = get_the_post_thumbnail($nextPost->ID);
            $post_tile=get_the_title($nextPost->ID);
            $thumb = wp_get_attachment_image_src(
            get_post_thumbnail_id($nextPost->ID), 'full' );
            ?>
            <div class="post-nav-thumb" style="background-image:
            url('<?php echo $thumb['0'];?>')"></div>
            <div class="post-nav-content">
            <div class="post-nav-subtitle"><?php next_post_link('%link',
            'Next Post'); ?></div>
            <h2 class="post-nav-title"><span><?php
           next_post_link('%link', $post_tile); ?></span></h2>
            </div>

        </div>
    </div></nav>

<div id="primary" class="content-area">
    <div id="content" class="site-content" role="main">
        <?php
            // Start the Loop.
            while ( have_posts() ) : the_post(); ?>

        <?php
                get_template_part( 'content', get_post_format() );

                // Previous/next post navigation.
                previous_post_link( '%link', 'Prev post in category', true );
                next_post_link( '%link', 'Next post in category', true );

                // If comments are open or we have at least one comment, load up the comment template.
                if ( comments_open() || get_comments_number() ) {
                    comments_template();
                }
            endwhile;
        ?>
    </div><!-- #content -->
</div><!-- #primary -->