hi there, your doctor could be right and it could be just GERD
or it could also be something serious like leucoplakia which needs to be ruled out by getting a biopsy
done. If you are a smoker or user of tobacco in any other form more the reason to follow it up. Do continue with the gargle tho' listerine
would be a better thing to gargle with. Visit a surgeon and get it cleared as to the nature of the lesion. If it is benign nothing further needs to be done. Take care.