They are the two skin folds that run from each side of the nose to the corners of the mouth. They separate the cheeks from the upper lip The area you describe could be identified as the naso-labial fold. These folds can get infected and cause dermatitis. It occurs following use of cosmetics, humid, sweaty climates, allergy tendencies. Also it is seen in obese individuals where the big cheeks make these folds deep and so predispose to infection. In your case I feel a simple low potency steroid cream, like Hydrocortisone cream with a antibiotic like neomycin cream ( Neosporin cream) would be helpful. Caution, if the pain increases / fever is present then u must see the doctor to evaluate the problem for systemic antibiotics and rule out diabetes. thank you jn