What Causes Pain In Ankle While Walking And Stretching The Foot?

Yesterday, I was riding a toy called a ripstik. It is like a skateboard with two parts held together by a bar that twists. When I was ready to get off, I stepped down from it while I was going pretty fast. A square edge from one of the pieces hit the side of my ankle back where my heel is. It left a huge knot that is sore to the touch and quite large. My ankle hurts when walking or stretching my foot. I have osgood schlotters disease (don't know if that's how you spell it) in that ankle and I'm wondering if I should be worried about fractures or anything like that. Please let me know as soon as possible.

-Alyssa Belford