For the Joomla single article page, you can try apply this following code into this PHP file.
JoomlaFolder/components/com_content/views/article/tmpl/default.php
You can take a look of my attached file where i put that following code into that PHP file.
[gist type="php"]
<?php
// call Komento comment model
$commentsModel = KT::model('Comments');

// Retrieve total rating for this particular article post (single article page)
$ratings = $commentsModel->getOverallRatings('com_content', $this->item->id);

if ($ratings) {
$totalRating = $ratings->value;
$totalRatingCount = $ratings->total;
}
?>
<div id="kt">
<div class="kt-ratings-overview" itemprop="aggregateRating" itemscope itemtype="http://schema.org/AggregateRating">
<div class="kt-ratings-stars" data-kt-ratings-overall data-score="<?php echo $totalRating / 2; ?>"></div>

<span class="kt-ratings-title"><?php echo JText::sprintf('COM_KOMENTO_RATING_OVERVIEW_TOTAL', $totalRating / 2, 5, $totalRatingCount);?></span>

<meta itemprop="ratingValue" content="<?php echo $totalRating / 2;?>" />
<meta itemprop="reviewCount" content="<?php echo $totalRatingCount;?>" />
<meta itemprop="bestRating" content="5" />
<meta itemprop="worstRating" content="0" />
</div>
</div>
[/gist]

But I am not familiar with Hikashop code so I do not know which PHP file render that single product page, perhaps you can consult with Hikashop developer regarding this.