That thing under my tongue is swollen do you know what that is?

Salivary glands: If the swelling is related to your salivary gland need to be evaluated for blockage , otherwise will result in infection.

Lots of things: There's lots of things under your tongue... salivary glands and ducts, blood vessels, and a lingual frenum.

Not without exam: Could be salivary gland or duct, frenulum, blood vessel, draining abscess, gum infection, lesion, etc. drop a dime, call your Dentist, make an appointment with the person who knows your mouth best.

Suspicious lump?: Regardless the cause... I would advise you to have the suspicious "thing"-lump under your tongue examined by a dentist or specialist (e.g. ENT, OFP). Any suspicious lump that does not resolve itself in 2-3 weeks should be evaluated.