There could be a number of reasons for your pain and a thorough clinical examination is necessary to rule them out one by one. It could be simply related to your surgery and radiation therapy as it can sometimes lead to inflammation of the nerves in this area leading to a neuritic pain that commonly radiates to the ear. It could be a local infection in the operated site compounded by the radiation. Worst possible, it could be a recurrence of your cancer. I would have liked to know the stage of your cancer as that would have helped me assess the risk of recurrence. I suggest you start on Tab Ciprofloxacin
500mg twice daily + Tab Paracetamol
650mg thrice daily + Tab Ranitidine
150mg twice daily + Tab Gabapentin
1 tab twice daily. That should take care of the pain and infection. Meanwhile get an appointment with your treating oncologist
and let him have a look.