When the side of your foot hurts it's usually because of a condition known as peroneal tendonitis.
The peroneal tendonitis can cause the side of your foot to hurt because the peroneal tendonitis causes the peroneal tendons to swell or become inflamed.
The causes of peroneal tendonitis can be the result of running too much, jogging too much or even because of an ankle sprain.
If you do continue to experience pain on the side of your foot you should see a doctor about it to be sure it's nothing more serious.
Most cases of peroneal tendonitis do resolve on their own without medical treatment but if the pain on the side of your foot continues for a week or more then see a doctor about it.