I'm An Active 47 Year Old Male. I Have Been

I'm an active 47 year old male. I have been road cycling consistently for almost 15 years riding about 6-8 hours weekly. Last Sunday, I drove 11 hours to Asheville for three days of cycling, about 3 hours per day of hard but not extreme riding. On Thursday, I drove home and was in the car for about 11 hours straight with only 3 short stops for gas. While unpacking Thursday evening, I developed serious pain in my inner thighs - the same muscles that will burn while cycling up steep hills. The pain became so severe that I could not walk for more than a few hundred feet. Sitting or laying down alleviates the pain within a minute or two but my thighs remain sore for some time. I've begun taking Aleve to help mitigate the pain. Two days later, it seems that descending a set of stairs will cause the pain/cramping in my inner thighs to return so that I have to lay down, rest for a few minutes, and then get back up. I have never experienced such pain from cycling. I have been sore after 8 hour days on the bike for special events, but not pain like this. I'm thinking it has something to do with being in the car for 11 hours after 3 days of cycling, but I guess I'm trying to rule out anything more serious.