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Hello,I am so sorry your boy is having trouble.
Without seeing him I can not say with 100% certainty but it sounds like your boy has a problem with the salivary gland.
These glands can become infected, clogged or damaged, a hands on exam will be needed to find the cause.
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In cases of infected or clogged glands often medication and draining the build up of saliva is effective treatment, however in some cases the gland needs to be removed.
I would suggest having him seen by your vet tomorrow this is not something that will resolve on its own.
I hope all goes well, please reply back if you have additional questions or concerns