A 45 year old male patient, a known case of left inguinal hernia presents to the emergency with an acute onset of pain abdomen associated with nausea, vomiting and abdominal distension. His pulse rate is $102$/min, BP is $100/70$ mm Hg and respiratory rate is $24$/min. On local examination, the skin overlying the swelling is tense and erythematous. There is localized tender- ness over the swelling; the swelling is irreducible with absence of cough impulse. The most probable clinical diagnosis in this patient is