What is the punishment for filing a false FIR against someone?

Yes. Filing a false complaint, or giving false information to a public servant with the intent to cause someone to be wrongly investigated or prosecuted, is itself a punishable offence. If it's established during investigation or trial that the complaint was knowingly false, the complainant can face criminal prosecution for that separately.

Beyond the criminal angle, you also have the option of pursuing a civil claim for damages for malicious prosecution, if you can show the case was initiated without reasonable or probable cause and with malice, and that it caused you genuine harm — to reputation, finances, or otherwise.

That said, simply having the original case eventually dismissed or resulting in acquittal doesn't automatically mean it was "false" in the legal sense required to prosecute the original complainant — that requires separately establishing the complaint was knowingly fabricated. It's best to first focus on your defence in the original matter, and discuss the possibility of these follow-up remedies with your advocate once that concludes.