I thought this was part of Boston soreness but it lingered on as the rest of the leg soreness faded away. During today's O it got worse after an hour of running - possibly due to a secondary injury - (pulled inner thigh muscle?)
Later: Decided this was a tendonitis type issue involving the adductor muscle and the hip flexor. But it is not clear cut. It's persistence is annoying. Still visiting PT (6/14/19).
Update: I accepted the alternative hypothesis of a hip labrial tear. After 3 months of virtually no healing my symptoms correlate with what's reported in numerous running blogs. If this is confirmed (MRI?) I would most likely need arthroscopic surgery.
I feel somewhat recovered (7/27) since I was able to do back to back mountain runs. But I still have lingering issues that require extra care with warmup, cool down, massaging etc. Also my running remains cautious at this point.