My foot was hit by a car like a week ago. it hurts a lot and now my ankle is too purple/blue. what should i do??

Time for an exam.: It sounds like there is some damaged tissue. You need to know the extent. After a week, the pain should have reduced, not increased. The safest thing to do is stay off of it and elevate it higher than your heart. It's time for a visit to a doctors for evaluation and x-ray.

Car vs foot: Get an evaluation, at a minimum you could have a fracture or severe sprain