Hello ,
Thanks for posting your query.

Sudden painful large growth under tongue can most probably be related to sublingual salivary gland which normally secrete saliva and can be swollen and painful in following conditions.

1. Sialolithiasis which means salivary gland stones which obstruct the opening of the gland.
2. Sialadenitis which means inflammatory swelling of the gland mostly infectious.
3. Viral or bacterial infections can cause pain, swelling , pus discharge from the gland. In addition, it can present with fever, myalgia etc.
4. Angioedema or allergic reaction to any food or medicine can also cause sudden swelling of lips and oral cavity.

In your case, if there are no other symptoms like pus discharge or fever or drug allergy, then the most likely possibility is either a stone or inflammation of the salivary gland.

Treatment would include antiinflammatory analgesics like Ibuprofen and if required antibiotics.

But before that you need to consult your doctor or dentist for palpation of the swelling, relieving of obstruction or drainage of any discharge if possible and confirmation of diagnosis. The further management would depend on the exact diagnosis.

Meanwhile you should maintain oral hygiene, do warm saline gargles for relief. If any history of allergy is present then, anti histaminics like Cetrizine might help.

Hope I have answered your query. Please accept my answer in case you have no follow up queries.

Regards.

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