I went through this last year. After months of pain, I finally went to the doct and to a PT. The diagnosis included mild arthritis in the hip joint (I'm in my early 40s), a bit of SI joint irritation, and what is affectionally called "dumb butt syndrom." My glutes had stopped firing normally and, as a result, other muscle groups had taken up the slack. I had also started to experience severe pain in my groin when I tried to open up my hip (like when sitting cross legged). I was never sure how or if they were all interelated. I went to PT for several months several times a week.
We focused on several things. I did a lot of exercises where I had to concentrate on engaging my glutes. For instance, I had to lay on my stomach and work on lifting my right leg by first engaging the glute. I also did a lot of bridge poses, clam shells and fire hydrant exercises. We also worked on getting more mobility in the joint. We started each session with the PT moving my leg around, sometimes in painful ways. I also did home exercises for this. Finally, we worked on a balance. I did a lot of stuff using the WiiFit.
In the end, 90% of my pain disappeared. It still took the better part of an additional year to get most of my mobility back. I can finally sit comfortably (well, for the most part) in a cross legged position.
If I were you, I'd get evaluated by a doc and, potentially see a PT. Don't do what I did and put it off. I suffered in pain far longer than I needed to.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher