Hello and welcome to HCM forum . In my opinion there can be multiple reasons for fever accompanied by pain in thigh. Following are some of the most common probable cause : 1.Acute Thrombophlebitis -A clot in the thigh vein , can be ruled out by getting a Doppler ultrasound of the leg . 2 .Psoas abscess--A large boil /abscess of the Psoas muscle . 3 .Nerve impingement / Sciatica --A nerve compression at Lumbosacral level can lead to various degrees of pain from thigh to calf . 4.Referred pain --Pain arising from the infection / inflammation of organs or joints other than the thigh itself . Patients typically experience a dull ache in the thigh that is poorly localized and may vary in severity or location. They may also experience pain or stiffness in other locations in the body such as the lower back, hip, groin or buttock. I would advise you to visit your GP soon ,as you might need antibiotics in case of case number 1 and 2 .