No one ever wants to hear “I told you so”. The other person is most likely aware that you told them so. The moment that you want to say “I told you so” is also the moment the other person has just realized that they were wrong. And that moment is not particularly enjoyable. In fact, they feel even worse because you told them so.
Saying “I told you so” makes you feel better. It expresses your knowledge and it satisfies your ego. It doesn’t help them.
You don’t have to say “I told you so”. You will find yourself thinking it, but you can also just keep quiet.