Ankle pain while running?

The specific cause seems to be that your body is not used to the distances and the hilliness of the routes you ran in the last 6 days. Why you feel the pain only in your left leg/ankle is because a chain breaks at its weakest link. For whatever reason your left leg/ankle is your weakest link under the stresses of the routes you've run in the last 6 days. This could quite possibly be shin splints which often occur when you run too much or too fast before your body is ready for it. I would ice the shins and perhaps take an over the counter pain medication.