Hip Pain

Anyone ever have an issue with their hip following a longer or harder ride? During the bike leg of my first Olympic tri this last weekend, my left hip joint was very sore. I say the joint but it feels more like the muscles right around the joint, whatever they’re called. It had happened once before during my longest ride to date (a little over 50 miles) two weeks ago. I train on a lot of hills up here in NH and the race course was very flat. I stayed in aero for probably 90% of the race and on the big chainring, something that I haven’t had the chance to do in training. The pain went away as soon as I was off the bike and got into a running rhythm. I’m guessing that it is a combination of my world class lack of flexibility , staying in aero much more than in training, and pushing hard because it was a race. Any ideas or just something that my body will adapt to?

Thanks