do_shortcode within a shortcode

You can try this:

add_shortcode( 'content','content_callback' );

function content_callback( $atts, $content = NULL ){
    $atts = shortcode_atts(array(
        'pid' => '',
    ), $atts);      

    if( ! is_int( 1 * $atts['pid'] ) )
        return "<!-- Shortcode Error: pid must be an integer -->"; 

    if(  absint( $atts['pid'] ) === get_the_ID() )
        return "<!-- Shortcode Error: pid can't be the current id -->"; 

    $queried_post = get_post( absint( $atts['pid'] ) );

    if( ! is_object( $queried_post ) )
        return "<!-- Shortcode Error: Post not found! -->";

    $postcontent = do_shortcode( $queried_post->post_content );
    $title = $queried_post->post_title;

    $finaloutput = $title . $postcontent;

    return $finaloutput;
}

where the shortcode is used like this:

[content pid="2069"]

where pid is some post ID.