Ankle Pain with No Swelling and No Bruising

I walked a bit too fast on the treadmill at my local gym a few weeks ago...and my ankle has been hurting me ever since. It feels like the entire ankle joint is hurting (even though there's no bruising or swelling). A friend of mine said my issues could be due to dehydration.

I stay home 98% of the time because every time I try to walk, my ankle cramps up, I get shooting pain from the bottom of my heel to the top of my ankle and I'm "hobbling" around. It got so bad that I can't even walk a block without pain.

What could be the cause of this immense pain? I live in a rural area and my roommate can't always drive me around so I'm forced to walk on a bum ankle making my problem worse.