Reg ~
I'm not a doctor and can't diagnose the cause of your pain from afar but it may have some connection to your AN surgery based on how you were positioned during the rather lengthy operation (mine went almost 9 hours). I didn't experience this kind of post-op pain - which does seem to be nerve-related - but you should consult a physician about finding some relief. There are many options to relieve nerve-related pain. From medicine to nerve-block injections to implanted electronic devices. I know this because my wife has suffered with nerve pain (due to spinal damage) that 3 different operations, numerous pain-blocking injections and a variety of drugs couldn't totally relieve. She now has an implanted device (in her lower back) that she controls with a 'remote' and that sends a very mild electrical 'charge' down her leg that blocks her nerve pain. It's a complicated deal but seems to be working for her. So, there is hope. Of course, in your case, the nerve-related pain may be temporary. That's why I advise you to see a doctor.
Jim