More posts from same cat -current one?

Thank u for ur time first and foremost!

My wordpress posts are split into categories. When u arrive at a specific post in the sidebar I’m trying to display more posts from that same category.

I am using:
query_posts("showposts=3&orderby=rand&cat='.$category_id");

Where $category_id is defined here:

<?php

foreach((get_the_category()) as $category) {
$category_id = $category->cat_ID . '';
$category_name = $category->cat_name . '';
	}
?>

The problem is that I notice the post I am viewing appearing in the randomly generated query on my sidebar. Is there a way to ensure the post I am on doesn’t appear within this query?

The beta can be seen here: Beta