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It sounds to me as if he could possibly have developed 'facial paralysis' which is a little like 'Bells palsy' in people.
It occurs when inflammation within the root of the facial nerve, which is the nerve that supplies the eyelid and lips, stops the nerve from transmitting the message to the muscles- so the muscles then become flaccid and lack tone.
He almost certainly needs to get veterinary treatment for this syndrome- as he probably requires anti inflammatory drugs to treat the potential cause of the inflamed nerve (possibly antibiotics too), but i would definitely get him checked at your vets asap.
I didn't realise you had a public holiday today!
It potentially could be fixed depending on the cause of the inflammation- if the cause is simply infection or inflammation, then yes he may respond well to medication- sometimes the underlying cause is a tumor(less common than infection) in which case the outlook wouldn't be good.