I had the same problem a few years back, it felt i had some sort of groin injury and i was had a bit of pain in my knee on the same leg, i presumed it was some sort of strain so i never really thought about it and presumed it would go away in a few days! But when it didnt go away after 3 months i went to see a doctor who then sent me for an x-ray, it turns out my femur bone was slipping out from my hip joint, the medical term for it is "slipped upper femoral epiphyses" i had left it for so long that it was impeading the blood flow to my lower leg!! I was rushed into surgery and i had a metal pin inserted into my hip through femur and into my hip to keep it there, a couple of weeks later it happened on my other leg and i had to go through the same procedure, i personally would reccomend that you go see a doctor just to be safe if the problems persist!