Ignis wants to prompt him to talk more about the said memories but... he also knows that they are terribly painful for him. There is nothing they can do to change them. Only try to live with them.

"If I knew this memory nebula thing has a high chance of happening, I would've advised you to stay away from going to the mission." Advised- not stopped. There's a difference.

He's silent for a few moments. "If there's anything troubling you, I'm willing to listen."