intervals

tonight i tried something new at the gym. i did an interval program on the treadmill. i lasted 10 min on an program of 3-6mph. i am really split on my opinion on it. on one hand it felt AWESOME! i wanted to keep running and running- but here's the problem: my ankles hurt badly after that 10 min and they still kinda do. i dunno if this is the kind of thing that will get better or if i'm just gonna get more and more sore if i keep it up. i don't want to make it so i can't run at all even on the elliptical, but at the same time i loved the intensity of that workout. thoughts? Please?