Dear Kirsten:
What you describe sounds like a mechanical problem and not a nerve problem per se. I think I would see a podiatrist or orthopedist. It may be that the tendon may get irritated with prolonged use or that there is a "catch" somewhere in the flexing or extending of your foot that is irritating you achilles tendon. You do not describe muscle weakness nor pain that radiates as one would expect with muscle or nerve problems. I would reserve surgery for the last ditch effort but only after seeing a orthopod or podiatrist.
Sincerely,
CCF Neuro MD