If the trip wasn't that long ago (meaning a few days), you could still have some eustacian tube dysfunction from the pressure change of flying through different elevations. The eustacian tube is a small tube that goes from your middle ear to the back of your nose. It is physiologically (normally) closed, and periodically opens up to let air go from the back of the nose to the middle ear. This usually happens when the pressure on the outside of the ear drum (tympanic membrane) is different then the pressure in the middle ear. If this tube isn't working properly, then the effects of pressure changes may be prolonged. Chewing gum, or nasal decongestants may help. My other main thought was that you could have either developed a cerumen (ear wax) impaction, or external ear infection
(otitis externa) from the ear plug itself. This would be painful, and may lead to purulent drainage from the ear. Either way, I would recommend making an appointment with an otolaryngologist
(ENT aka Ears Nose Throat) physician to get your ear checked out. Best of luck.