thanks for your query.
I thinks its a Eustachian tube dysfunction
Take nasal decongestion drop like otrivin
or orinase nasal drop for decongestion of nasopharynx
and Eustachian tube area.
Along with that take antihistaminics like Fexofenadin tablets and mucolytis drugs like acetylcysteine
Take steam inhalation atleast 2 times a day that will increase mucociliary clearance.
Do not Blow the nose forcefully or avoid swimming or air travel for few days.