The heat in your feet which u are feeling could be as a side effect of chemotherapy
drug like oxaliplatin
used in your chemotherapy schedule which is used frequently to treat colon cancer
and is called peripheral neuropathy
It will take 6 months to 1 year for the heat to go away totally.
U can take T.Pregabalin 75 mg twice daily after food for 3 months which may help somewhat.
For thyroid growth do USG of thyroid and if mass found then FNAC from it to determine whether it is benign or malignant.
Regards and take care