It may be phimosis if the foreskin is unable to retract over the head of the penis due to tightness, as per your symptoms. Swelling and discoloration could result from irritation and infection caused by the trapped foreskin. The thigh pain could also be linked to this issue or possibly a different problem altogether. An examination by a urologist is necessary. The tests that may be carried out include blood tests for infection, urine tests, and a physical examination of the affected area.