Kotoba no Hibiki

Let me tell you something

By

A: What’s wrong? You have an angry look on your face.
B: I saw him walking with a girl yesterday.
A: Aha, but she could be a colleague or something.
B: Let me tell you something, I’m not the jealous type.

In this situation, what should you say “Let me tell you something” in Japanese?

Casual

B：言いっとくけど、

Note: This is not a word-for-word translation.

Advanced Tips

A word-for-word translation

B：何なにか言いわせてください、

It’s a bit weird in Japanese. It’s not grammatically wrong, but I don’t think we say it.
In this context, 言いっとくけど is natural.
In the situation where you want to say something to interrupt someone, you could say ちょっといいですか？.