How can you?

How can you tell someone you think they are lying to you, when you are doing somethign you really aren't supposed to do. I guess you could say I'm a bit deceiteful, but I don't do it to hurt anyone. I do it cuz I'm nosy.

I am very upset right now, because I think I'm being lied to. If I confront the person, I have to admit something I know that they won't like. I have to admit, I'm nosing into their things again.

Which is worse? Is it ok to let the lie go?