B..
I did almost the same thing about 30 yrs ago. I was coming down the steps and the bottom one wasn't even 2 inches tall but I hit the side and turned my foot. Severe sprain. It was niclely red and purple which means torn ligaments.
You could have a chiped bone or not. Keep ice, no heat on it. Keep off of it entirely. Ibuprophin.
You would probably be fine if you waited till Monday to see a doc. I was put in a walking cast for 3 weeks.
ETA: glad it was just a sprain but treat it with care just the same!