Probably the pain could have caused by friction and you never noticed it when occupied but when not it Rs noted indicating some amount of psychosomatic response. I would ask you to take it easy unless the pain is moderate or there are other symptoms. Kindly just see a good urologist for the same if the need be which I don't think, however unless we know your medical history and have done your physical examination we won't be able to pin point 100% either. Please relax. The pain is most likely to subside on its own don't read too much into it. All the best.