The impact might have damaged the fascia that runs along the bottom of your foot. It was unclear exactly what type of pain you were feeling.
It sounds like you might have a heel spur.
http://www.heel-spur-treatment.com/pages/plantar_fasciitis_exercise.php
I found this site and they offer some good advice on what causes heel pain and some stretches and exercises to help too.
That being said, you really need to see a medical professional if your heel keeps hurting. I think they even have a free guide.
I hope it helps.
