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?
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.
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.