If you have 'niggles' or pains the first thing to do is stop. Pain is usually the body's way of telling you something is wrong. When you have no pain walking around, don't go out and do your usual run, but try jogging for a minute and walking for a minute a few times on soft ground to test it out. If you have no pain the next day then you can gradually build back into your training. If the pain doesn't clear up within a day or two, think about going to see a physiotherapist for an assesment and recovery plan.