While some amount of soreness is expected, if it persists or if the pain is quite high, the following could be some of the reasons:
1. Wrong Shoes: Ensure you are wearing Quality Running Shoes… They are designed for Running and will keep your Feet Stable and provide a good cushion from the Impacts of Running.
2. Old Shoes: Even if you are wearing the right kind of shoes, ensure that you replace the shoes, after the recommended mileage. Shoes that used to work well, will not be able to continue to provide adequate support, once it’s usage is past the Recommended Mileage.
3. Wrong Size Shoes: For Running Shoe size, you will need one or two Sizes more than your Normal / Regular Shoe Size. This is because, your Feet Expand while Running, especially, if you do a LOT of Distance Running.
4. You are Running Too Much Too Soon. Design a proper Training program for Running and stick with it.
5. Improper Running Posture: This is a vast, but quite important topic. Lots of articles on the Internet to lookup.
6. Improper Running Surface: Try NOT to run on Extremely Hard Surfaces such as Concrete. Road Running is a little better (with the proper shoes on). Running on grass is likely the best, as far as minimizing impact from Running. However, if you are Running Long Distance, that would not be possible. Running on Trails and on Beach Sand is going to take a LOT more effort and will be a HUGE strain on your Ankles, Knees and Feet.
7. Ensure that you are taking in adequate Nutrition, in terms of Carbohydrates for Energy Replenishment. Adequate Protein is also vital for Repairing / Recovery of your body, from the Strains of Running..
8. Stay Hydrated: You need to ensure that you stay adequately Hydrated. Don’t even wait until you feel thirsty. Keep drinking water regularly…much more so, if it gets Hot and Humid.
9. Replenishing Salts are important too. If not you will suffer from Cramps and will impede your Recovery.
10. Proper Rest and Recovery is Very Important too. You cannot do too much and not give your body enough time towards Rest and Recovery. Otherwise, you will be heading into Over Training, which will then have a VERY BAD EFFECT on you.
Hope this helps!