Thank you very much for contacting healthcare magic. You have problem of sudden ankle pain that may be because of muscle spasm mostly. Heat pad or warm towel application give relief in pain. You don t mention any swelling or redness over ankle region present or not. If swelling and bruishing over ankle area present than you have to contact a physician for further diagnosis. Any injury may cause ankle pain and swelling. Poor blood supply may cause pain at ankle region. Nerve compression may cause pain . X ray of ankle region helpful for further diagnosis. Consent a physician for further treatment. I hope my guidance is helpful to you. Thank you very much.