For pain in leg here first you need to check either it's at knee level or at calf muscle level. If it's close to calf muscle level then check with squizing calf muscle belly and if it pains then it can be related to vascularity it issue of lower limb and dopler test is needed. But if this is negative then it may be only over use injury.
Now if pain is only at knee level then again need to check with few physical test. As a conservative treatment management you can use hot and cold pack at pain full area with rest for few days and avoiding any activity which pains. But if it does not give pain relief then visit a good physio and orthopedic who can check with physical test and evaluate the problem as well guide you with treatment and exercise program. Follow the advice and I am sure it will be useful. Take care