The lump is sure due to soft tissue as there is nothing on an X-ray. Rule out skin lesions like infections, sebaceous cyst, varicose vein, scar tissue, foot injury, gouty tophi or ganglion cyst. It can also be a ligament or tendon injury. Follow up with a physician for a proper diagnosis.
good morning Mom, just wasting time and money going to a family doctor, i would suggest a Podiatrists they specialize in feet and ankles. good luck Phill