What Causes Huge Knot On The Right Leg Calf?

Hi - I am 60 year old female. Just finished chemo for rectal cancer and also had my lower left lobe removed due to lung cancer. They were not related. My right leg calf has a huge knot and is now causing my leg to feel tingly and the top of my foot numb. Should I be concerned? I do not have a doctors appt w/oncologist for 3 more weeks. Thanks.