Your cause of action would be "assault and battery". Call a lawyer.
[In accordance with the Avvo community guidelines, this communication does not constitute "legal advice", nor does it form an attorney-client relationship.]
Do not delay calling a attorney in the state where this incident happened. Many states limit the time you have to file suit and also require that you file a claim first.
The above is not intended as legal advice. The response does not constitute the creation of an attorney client relationship as this forum does not provide for a confidential communication.
Typically, that kind of lawsuit would be brought in the state where the officer abused you. If you intend to file in Tennessee, you must do so immediately as Tennessee has a one year statute of limitations. This means, if you let more than a year go by from the time you were assaulted, you lose the right to sue the officer or the police department. Other states have different time limits. Contact a lawyer in that state immediately to see if you have a valid lawsuit.
Nothing in this communication should be construed as creating an attorney-client relationship. I provide this service for educational purposes only. I will take no action on your behalf unless you have hired me and a written retainer agreement is signed. I am licensed only in Tennessee and I strongly suggest you consult with an attorney in your city and state as Statute of Limitation deadlines can limit your recovery.