A 48-year-old woman came to a dentist with complaints of a painful ulcer on her tongue. She had a similar ulcer one year ago Objectively, on the lateral surface of the tongue there is an oval erosion up to 5 mm in size, covered with a fibrinous plaque, surrounded by a hyperemic margin, soft and sharply painful to palpation. Oral mucosa in other areas is pale and edematous. What diagnosis can be made in this case?