Make sure your shoes are not to old. Some people wear the same shoes for years, which is not good. If you are walking a lot you must make sure the arch support is adequate. It definitely sounds like inflammation.
Thanks for responding. I normally wear tennis shoes - either Nikes or New Balance. I don't wear heels that often. I take long walks for exercise, maybe I twisted my foot or something. The pain is more in the arch instead of the heel. I'll try stretching my foot, I haven't done that yet. I did ice it for the first couple days.
Sounds like Plantar Fasciitis; my guess.
Try stretching the foot, ice, rest and an OTC NSAID, i.e Motrin.
What kind of shoes do you wear daily?