ても知らない【てもしらない】

ても知らない is a warning: "don't blame me if ~", "it's not my problem if ~". It follows a verb's て-form, and that verb is the bad thing that will happen if the listener carries on. しらない知らない here means the speaker washes their hands of it, not that they don't know.

A first clause with なら, と or a て-form says what the listener is doing wrong, and ても知らない gives the consequence. It ends with よ, からね or, rougher, ぞ.

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The speaker has already given advice and is now giving up on it – a parent to a child, friends, partners. It sounds exasperated, so it is not said to someone above you. The polite しりません知りませんよ exists but is still blunt.

In casual speech ても becomes たって.