Achilles tendon

get a bike with some gears and don't push it. just cruise.
if i were you i would:

• stop riding fixed for the moment, wait a few days until swelling has calmed down
  
• go on the geared and cruise (no high spin or no high gears) take it really slowly
  
• hopefully you havent royally screwed it over so it should be able to take that ^ if not go see your GP asap to see what they have to say