Unexplained ankle swelling…? and PAIN!

I first noticed a slight pain occurring in my left foot and simply adjusted my shoe and continued working.
A bit later I realized that my foot was really hurting, so I took my shoe off and realized that it was very swollen.
I thought I had been biten by a spider possibly, but there is not a visible bite.
It has only been a day, but the swelling has been increasing.
The pain is centralized in the outside of my ankle bone area and my entire foot is largly swollen – even my toes.
I think my calf is swelling and it definatly hurts. And finally, there is a strange tightened area running up my calf – its weird – oh yeah, my foot is warmer than usual and when I put pressure down on my foot my toes become numb.
I don’t know whats going on – I hope you can help –
thank-you for your time and insight CAB – [email protected]