Middle Ear Hematoma or Serous Otitis Media: This is the most likely diagnosis given the history of a bar fight, which could have resulted in a direct blow to the ear or a blast injury causing a middle ear hematoma or serous otitis media. Both conditions can lead to muffled hearing.

Temporal Bone Fracture: A fracture of the temporal bone could occur from a significant blow to the head, leading to symptoms such as muffled hearing, vertigo, and potentially facial nerve paralysis.
Ossicular Disruption: Trauma to the ear can cause disruption of the ossicles (the bones in the middle ear), leading to a conductive hearing loss.
Eustachian Tube Dysfunction: Trauma or the aftermath of a fight could lead to Eustachian tube dysfunction, causing muffled hearing due to the inability to equalize ear pressure.

Perforated Tympanic Membrane: A perforated eardrum can occur from direct trauma to the ear and must be diagnosed and treated promptly to prevent infection and further complications.
Cerebrospinal Fluid (CSF) Leak: Although less common, a temporal bone fracture could lead to a CSF leak, which is a serious condition requiring immediate medical attention to prevent meningitis.
Intracranial Hemorrhage: While less directly related to the ear, any significant head trauma could result in an intracranial hemorrhage, which is a medical emergency.

Labyrinthine Concussion: This is a rare condition where the inner ear is concussed, leading to symptoms such as vertigo, tinnitus, and hearing loss.
Traumatic Meniere's Disease: Although rare, trauma can trigger Meniere's disease, characterized by vertigo, tinnitus, hearing loss, and ear fullness.
Ototoxicity from Trauma: Certain types of trauma could potentially lead to ototoxicity, although this is more commonly associated with certain medications or chemicals.