What Causes Tingling And Numbness In Bottom Lip And Chin?

+Hi, my bottom lip and chin on my one side went tingly/numb one week ago. This is not due to a dental problem (my dentist did an x-ray). I have seen my GP (there is some feeling there) and am due to see my oncologist late today - I had a mastectomy 18 months ago, have had chemo and radiotherapy and am on arimidex. I have googled and am scared by what I read. Help!