Recent research seems to show that hip flexor mobility and strength is more important in runners than once thought. For this reason, I encourage everyone to complete a Myrtl routine on a regular basis (at least twice a week).
However, sometimes even despite our best efforts we will get injured. See below for stretches and strengthening exercises
Myrtl: As mentioned before, it is a great basic mobility routine.
A-skips and B-skips: Done to improve running form and utilize the hip more. Proper form can be seen in the video here.
All of the above exercises, and:
Ice: ice the location
Hip Extension in Lying:
Begin lying on your back, with your buttocks at the very edge of a bench or bed. Take your good knee towards your chest as far as possible, letting your injured leg drop down towards the floor (figure 3). Hold for 2 - 5 seconds at a mild to moderate stretch and repeat 10 times provided it is pain free.