Is it unusual to have a middle ear infection after an inner ear infection?

Clarify: Inner ear infections are rare and would involve the hearing and balance part of the ear with resultant deafness and severe vertigo. Rarely middle ear infection can spread to inner ear. Most likely you had a middle ear infection which when treated has residual fluid behind the ear drum. This fluid usually clears but if there is still hearing loss after 3-4 months then see ent.