site navigation mistake

Hi! I am brand new to WordPress and coding. I’ve successfully created a child theme and altered some layout and am very proud of myself, but I’m having an issue I don’t know how to fix. (I have several things I haven’t figured out how to change, but this one seems to be a mistake in the original theme.) I’m using the Spun theme as a portfolio site. Once you are into the post there are navigation arrows on the left and right sides to take you to the previous or next post. The problem is, when you click ‘previous’ it takes you to the ‘next’ post and vice/versa. I can see this in the HTML, but I don’t know the proper way to fix it:
<div class=”nav-previous”>

<span class=”meta-nav”>?</span>

</div>
Could I just replace the URL with the one that is actually previous? Where in my child theme (would I put the new code?

Thanks!