I am currenlty recovering from this injury. My physio diagnosed me right at the start - said it was all due to my tight hamstrings which is due to my weak core.
So treatment was to stop running for 10 days whislt doing 5 sets of 30second planks, 3 times a day. In addition to this, I also stretch my achillies twice a day my raising onto tiptoes etc.. 6 weeks in and I am gradullay bringing up om mileage - by leaving at least 24 hours between runs. So I cycle one day and run the next