Edit links in Dynamic Sidebar

Hello i have a problem

I have a dynamic sidebar, thet puts the list of categories an latest posts to my site as a menu.

In html it looks like this

<ul class="nav3-grid">
			<li id="mycategoryorder-2" class="widget widget_mycategoryorder"><b class="widgettitle">Categories</b>		<ul>
			<li class="cat-item cat-item-1"><a href="https://site/category/first/" title="first">First</a>
</li>
	<li class="cat-item cat-item-13"><a href="https://site/category/second/" title="Second">Second</a>
</li>
</ul>

What i want to do is to add “nofollow” parameter to the links, to make it look like:

<li class="cat-item cat-item-1"><a rel="nofollow" href="https://site/category/first/" title="first">First</a>
</li>

but i can’t find how to do it. Thank you