What Causes Pain In Groin And Back Muscles After Strenuous Physical Exertion?

I experienced nearly immediate pain in the right groin, lower back right side and muscle in upper back of right leg following a strenuous doubles tennis match. I am a very active 72 year old who spends 3days a week on the court,walk over two miles each day (I have a large lab who requires a lot of exercise) and I line dance once a week. This pain has me nearly on the couch and when I rest I get stiff beyond words. When I walk I feel the pain increasing. So far just taking two Advil twice a day but the discomfort is increasing. Would appreciate a response from an mad in orthopedics Maggie Scatchard