it sounds like I had the same thing as you. Basically you've got tendonosis, which is legions in the tendon so there shouldn't be any swelling. There is a good exercise where you stand up on your tip toes and then very slowly lower down on the foot with the bad heel. Do sets of 3x15, 3 times a day. If it gets too easy, add weight otherwise the exercise won't do anything. Lots of calf and hamstring stretches are good too. If it gets any worse, go and see a physio and maybe get some acupuncture.