A 40-year-old woman had lower third molar extracted due to dental caries. Then she developed high fever and pain. On examination, tonsil deted medially and there was swelling in upper one-third of sternocleidomastoid muscle, Most likely diagnosis is:

Abscess of pharyngomaxillary or lateral pharyngeal space is also known as parapharyngeal abscess. Infection can come to this space from acute or chronic infections of tonsils and adenoids, bursting of peritonsillar abscess, dental infection of lower third molar teeth, Bezold's abscess, petrositis, infections of parotid, retropharyngeal, and submaxillary spaces, injuries of neck etc. Fever, odynophagia, sore throat, toicoilis and signs of toxemia may develop.