Ankle and foot painful after running?

For a bout a year now I get this mild sprained ankle pain on my ankle and top side of my foot after I go running. Some times I get mild bruises at the top of my foot. I have rested it twice for 6 weeks at a time but it still occurs. I use an ankle sports support sock- it still aches after even a small run. I've just joined a gym and the reason I joined it was for the treadmills so what should I do?