I forgot my lmp, and I'll having a check up this week. I know the nurse will interview me what will I'm going to tell them if when was my lmp?

You tell them the truth. You don't remember.

Or is this a trick question?

You tell them the truth. You don't remember.

Or is this a trick question?

Nah! Im serious. I really forgot it, will they scold me?

Scold you? No. You forgot. It happens.