wp_reset_query() will reset the query to the original query WordPress did on this page. So if you somewhere called query_posts(), it will not reset back to that query, but to the “main” query.
You probably want to use wp_reset_postdata(), which resets the $post variable to the current post in $wp_query.
The best thing is to not overwrite the global $post variable in your function. All WordPress functions have variants that accept a post object, so there should be no need to use the global variable there.