Rest ankle. Its best to not bear weight on the ankle and rest it up. If there is swelling, cold pack and elevation will help reduce some of that. An elastic (ace) wrap or neoprene support may also be helpful. If the pain continues, see your doctor.
See your doctor! Its important to have a physician look at your ankle esp if you're a runner because it can be anything from a sprain, pinched nerve, inflammation, etc. Avoid putting weight on it if that reproduces the pain, but consult a doctor. Also, a qualified running coach can evaluate your gait and advise you about ways to make your running stride less traumatic. Make sure you have good supportve shoes.