A 3-year-old child comes to with the complaint of fever, malaise, and oral ulcers due to which swallowing is difficult for the child, what could be the possible diagnosis?

Primary herpetic gingivostomatitis: Caused by the HSV-1. Occurs most often in infants and children younger than 6 years of age. The disease occurring in children is frequently the primary attack and is characterized by the development of fever, irritability, headache, pain upon swallowing, and regional lymphadenopathy. Within a few days, the mouth becomes painful and the gingiva which is intensely inflamed appears erythematous and edematous. The lips, tongue, buccal mucosa, palate, pharynx, and tonsils may also be involved. Yellowish, fluid-filled vesicles develop. These vesicles rupture and form shallow, ragged, extremely painful ulcers covered by a gray membrane and surrounded by an erythematous halo. Ref: Shafer's textbook of oral pathology 7th edition page 342