Store value in cookie

Use setcookie() like shown below:

setcookie(
  $name, 
  $value, 
  time() + 3600, 
  COOKIEPATH, 
  COOKIE_DOMAIN
);

Note:
$wpdb->insert_id AFAIK will always return false or 1, so I’m not sure if that will be of value for your. I might be wrong about that see @s_ha_dum’s comment.