Display a custom name when the user has no name settle in his account

Use PHP ternary comparsion operator to check if get_user_meta() function returns blank or non-blank result:

function colaborador_nome($atts) {
    if (is_user_logged_in() && !is_feed()) {
        return '&nbsp;'. (get_user_meta( get_current_user_id(), 'first_name', true ) ?: "Hi >No Name<, please settle your name in your account.");
    }
}
add_shortcode('colaborador_nome', 'colaborador_nome');