What Causes Persistent Pain In Leg?

Hi,For the past three wks or so I've had a pain in my leg. It goes from the hip and runs down to my knee, outside leg.I thought it may of been muscle strain but it hasn't gone away. It feels tender, like a bruise or the bone is sore but I have no marks what so ever on the skin. When I sit on the ground, it takes a few steps for me to get upright but even walking is becoming painful in the hip. Should I be worried?