Aren’t you just a tinsy bit curious?

[Aaron]

Janice: Well umm, I thought I was going to go back to my apartment but then I just felt I couldn’t really be alone tonight. (Joey walks into view of the open door behind Janice, sees her, gets a terrified look on his face, and flees in horror.) I was wondering if I could maybe stay here with you, just I really feel that I need to be with family.
Monica: (To Chandler) Our kids are gonna call her Aunt Janice aren’t they?
Janice: Please, it’s because otherwise I really don’t know what I might do.
Chandler: Aren’t you just a tinsy bit curious?

=>
I have no idea why Chandler said that and does that even means?

[Casiopea]

"I really don’t know what I might do" is another way of saying, "I'm so depressed that I might do something I'll regret, something like kill myself." Chandler's reply, "Aren't you a tiny bit curious" is on the positive side; it's in reference to things that we have done that we later regret having done but were fun to do at the time; e.g., sleep with a stranger, get a tattoo while drunk, etc.)

[Aaron]

Wow, that's so amazing! I had no idea what it might mean. Thank you so much! It's was a thing that I would never understand unless there wasn't your help.

[shane]

If I can just add something:

The joke here is that Chandler and Monica loathe Janice, and so when Janice says she doesn't want to be alone at home because she doesn't know what she might do (like commit suicide), Chandler's words are meant to mean, "please don't stay with us. Go home and find out what you might do!"