Thanks meshellmybell2008! Cool name too!
It is possible that you have strained the muscle in the bottom of your foot. If you stepped onto a rounded surface like a curb you could have stretched out the muscle. That is what happened to me and it sound pretty much like the same symptoms. I would suggest alternating heat and cold, giving a few days to rest, if you are still having a problem or the pain becomes extreme I would suggest going to your doctor and having them take a look at it.
The foot and ankle are made up of many small bones. In between these bones, like any other joint like your knee or hip, there are small pads of cartilage that cushion the space between them.
Over time, these pads can wear away (osteoarthritis), and when the bones grind together it causes pain. I'm not saying this is what's happening, but it's one possible cause.
What causes the majority of the pain is usually the side-to-side rotation of the foot/ankle, not so much the up/down motion of flexing and extending the foot. Often the pain seems to travel up to involve the ankle and lower let. A custom-made ankle brace, one that allows your foot to flex up and down normally, but stabilizes and prevents rolling in and out, can be a big help.
Surgery to insert stabilizing pins through the offending joint(s), thus fusing them, does internally what the brace is doing externally, allowing you to get rid of the brace.
I had the pins put in my right foot and currently have the external brace on my left. The brace does a good job so far, so I've put off surgery on the left.
Diagnosis involves visiting an orthopedic surgeon (NOT a podiatrist!) and having x-rays. From there you can decide what course of treatment to pursue - either the non-invasive brace and/or shoe inserts (orthotics), or surgery.
Note: the doctor may want to put you in a fixed brace, which will not let your ankle move at all. Personally, this did not work for me, because it threw off the way I walked, which in turn caused pain in my knee, hip and lower back. The next time around, I insisted on an articulated brace. The doc wasn't happy, but I stood firm because I knew what would work best for me.
Hope this helps!