just saw this thread. Sounds like something is trapped - a visit to an osteo might help. In the mean time, stretch your thighs with bending at knee and tucking foot up to your bum.

Hip flexor stretch - there are a few but the one I find best is to kneel as if you're proposing to someone, then lean forward straightening the back leg (hope that makes sense).

Also try to stretch your glutes. The one I find best is to stand (most people can achieve the same stretch sitting but I am double jointed), bend the affected leg so your ankle is above your knee. If your standing, hold on to something and then move as though you're going to sit. If you're sitting, you might need to lean forward from the hips to achieve the stretch.

Oh, and I'd probably try some anti inflammatories. I take oral voltaren which can be purchased over the counter at the pharmacy.

HTH and hope it has settled

MG