RhinoRunner says:Generally, when people complain about "hip" pain, they are identifying the area of the Greater Trochanter. That's the bony protuberance on the outside of the upper leg below the pelvic crest. Hip joint dysfunction, primarily variations of arthritis and degeneration, are described as "groin pain". So, I'm going to assume you are having your symptoms at the outside of the upper leg.
Often what happens to people who have been running for awhile and develop this type of injury is that something in the running mechanics break down. The support in your shoe can break down, bad habits develop like turning a foot in as you run, compensation from other aches/pains/injuries occur, fatigue with increases in training volume and/or frequency.
I recommend:
1) Stretch the hips in all planes
2) Strengthen the hips in all planes (resistive bands or ankle weights)
3) Work the tissue. See a massage therapist for sport or deep tissue work, or use a foam roller. It's going to hurt, but go really slow and work small areas at a time. Go as deeply into the tissue as you can tolerate. Even getting someone to work a rolling pin over the area can help.
4) Ease back into running while paying attention to your mechanics.
If you don't know where to begin on exercises and stretches, see a physio/physical therapist. Don't let this go and wait for it to go away by itself. Get it taken care of and get back to your life.
Good Luck!