How to say "open Pandora's box" in Japanese?
When I asked Jane about her problems, I didn't know I had opened Pandora's box.
What kind of Pandora's box do we open if we decide not arrest people who have committed a crime?
Sorry if you expected something cooler. You can say this in Japanese and be understood, however the norm might be to phrase it in a more direct way.
If you want a more Japanese equivalent, this entry from the link above has a few alternatives:
open a Pandora's box
It's possible that there are other Japanese idioms that capture this same meaning that I don't know about. You'll also be totally fine avoiding the idiomatic use and just saying it directly (so for example talk about how you made Jane upset or whatever problem happened as a result of asking about her problems).
In case anyone (1 yr later) should reference this, one good idiomatic expression is "yabuhebi", not quite Pandora's box, but a dangerous snake that lies in the grass and should not be stirred up -- because once stirred it will not ignore you. This expression is used very commonly in Japanese, e.g. "それを言い出したらやぶへびだよ。やめたほうがいい。”