previous_post_link and next_post_link only on individual post

Hi! ??
I own this website,
https://www.runtimecomics.com/ (only +18)
and I have previous_post_link and next_post_link template tags, but they are shown in the homepage and individual posts. How can I do that they only show in individual posts? (not in homepage).
There’s no single.php file in the theme, so I don’t know how to make it…
Any help? Thanks in advance! ??
This is the code of index.php:

<?php get_header(); ?>
  <div id="bd" class="yui-navset">

    <div id="yui-main">
		<div class="yui-b" >
			<div class="yui-ge"><div class="yui-u first">

	<?php if (have_posts()) : ?>

		<?php while (have_posts()) : the_post(); ?>
<!-- item -->
<!--noshare-->
				<div class="item entry" id="post-<?php the_ID(); ?>">
				          <div class="itemhead">
				            <h3><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a></h3>
				            <div class="chronodata"><?php the_time('F jS, Y') ?> <!-- by <?php the_author() ?> --></div>
				          </div>
						  <div class="storycontent">
								<?php the_content('Read more ?'); ?>
						  </div>
				          <small class="metadata">
			<span class="category">Archivado en: <?php the_category(', ') ?> <? if(!is_single()) echo "|"; ?> <?php edit_post_link('Edit', '', ' | '); ?> <font face="arial"><font size="3"><b><?php comments_popup_link('?Comenta!', '?1 Comentario!', '?% Comentarios!'); ?></span></b></font></font>
<IMG SRC="https://www.runtimecomics.com/botones/bcomenta.gif">
<?php if ( function_exists('wp_tag_cloud') ) : ?>
							 <?php the_tags('<span class="tags">Etiquetas: ', ', ' , '</span>'); ?>
<iframe src="https://www.facebook.com/plugins/like.php?href=<?php echo urlencode(get_permalink($post->ID)); ?>&layout=standard&show_faces=false&width=500&action=like&colorscheme=dark" scrolling="no" frameborder="0" allowTransparency="true" style="border:none; padding-top:2px; overflow:hidden; width:650px; height:25px"></iframe>
							 <?php endif; ?><br>
<b><?php previous_post_link(); ?></b>
<span style="float:right"><b><?php next_post_link(); ?></b></span>
						  </small>
				 </div>
<!-- end item -->

<?php comments_template(); // Get wp-comments.php template ?>

		<?php endwhile; ?>
		<div class="navigation">
                        <b><font face= arial><font size=4>
			<div class="alignleft"><?php next_posts_link('? Cómics anteriores') ?></div>
			<div class="alignright"><?php previous_posts_link('Cómics siguientes ?') ?></div>
                        </font></font></b>

		</div>

	<?php else : ?>

		<h2 class="center">?Joder, no se encuentra la página!</h2>
		<p class="center">Lo siento, lo que buscas no está aquí. Sigue buscando xD!</p>

	<?php endif; ?>
<!-- end content -->
<!-- 2nd sidebar -->
</div><!-- end yiu-u --><div class="yui-u" id="third"><?php if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar('rightsidebar') ) : ?><h4>Extra Column</h4><p>You can fill this column by editing the index.php theme file. Or by Widget support.</p><?php endif; ?></div>
<!-- end 2nd sidebar -->
			</div>
		</div>
	</div>
	<div class="yui-b" id="secondary">

<?php get_sidebar(); ?>
	</div>
  </div>
<?php get_footer(); ?>