A quick checkup at the doctors is in order!

Probably just a cheap prescription for antibiotics will cure it real fast, did for me.

Untreated bad things might develop.

I have the same thing. My right tonsil was enlarged and my lingual tonsils from hayfever and related post nasal drip. Of course ENTs have to say lymphoma could be a differential diagnosis. I took antibiotics and it shrunk, but it I skip my antihistamines or sleep in dry air conditioning, I feel it swell. I have a deviated septum that shunts the post nasal drip primarily over the enlarged tonsil, causing it to be inflamed. Removing the tonsils won't cure the post nasal drip, but it will stop the inflammation of the palatine tonsils, but in my case, it won't stop, but might increase the inflammation of the lingual tonsils at the base of the tongue. One ent told me that if the increased tonsil is due to allergies, the only way to shrink it is with coritizone but they won't give it to you while they are watching to see if it is lymphoma because it could shrink it even it was lymphoma, so I wait three months to see it if doesn't get bigger and allergy season ends and see if it gets smaller- the ent said it may never get smaller- and then take a little cortizone or have the tonsils out for peace of mind and the ent said it will be a continuing problem with the allergies.