How can I tell if I tore a ligament in my ankle?

Last week I was walking and as I was coming off of the curb I twisted my ankle and fell on it really hard. I hear a fairly loud popping noise and couldn't walk for a few hours. It's been a week since this happened and it still hurts a lot. It was swollen for a day or 2 but now it is not. There's no colour difference either. In the morning when I wake up it usually hurts up to my knee when I put pressure on that foot but that stops happening after a couple of hours. Did I just sprain it badly or is something else wrong?