function sk_add_logo_left_primary_nav( $nav_output, $nav, $args ) {
    $logo = 'Logo HTML comes here';
    $nav = $logo . $nav;
    $nav_output = $nav_markup_open . $nav . $nav_markup_close;
    return $nav_output;
}
add_filter( 'genesis_do_nav','sk_add_logo_left_primary_nav', 10, 3 );