Bone lesion found in xray of knee. im worried. could this be cancer? what could b the causes of bone lesions?

Bone lesion: There are many potential things here, and a malignant tumor is one of the least likely things at your age. Cysts, infection, numerous benign lesions and the rare cancer can all present as a radiographic finding. A good radiologist will be able to give the likely possibilities, but if a biopsy is needed, many of these require someone with significant experience with bone lesions.