Ah, but how would they know? Could be something you got from the cramped flight? Sounds like a nerve though. I have the thigh thing sometimes, but it usually goes away within a week at most. There are creams that heat up maybe try some of those on your back before you go to sleep, they help a lot to relieve the pain. There's tons in Japan and a few in Germany as well or you can ask at the pharmacy. They're not too expensive. Just take one that heats up there are also creams that cool.

Have a good flight!