No, it isn't. It's nothing. It's no big deal, really. Asriel wants one of those sentences to reach his mouth, but instead:

"It's when I woke up as a flower - the first time. I tried to make the memory stop, but it just kept going."

No matter how many times he ripped that flower version of himself out of the ground, no matter how much he pleaded with himself to just shut up, it would always come back, crying for help that would never come.

He'd also rather tear his own tongue out than keep talking about it. He's still not entirely sure what Chara does and doesn't know about Flowey, but the less he talked about it, the better.

He doesn't want to be remembered as Flowey. He... doesn't have to be, right? If he just doesn't get angry like before, if he buries all those sarcastic remarks that sometimes pop into his head, if he just buries those destructive urges, all of it... he won't be.

But everyone already knew who he was.

Asriel tries to quickly change the subject.

"I'm making hot chocolate. Well, I was trying to before I knocked over a bunch of pots.

... Do you want some?"