What is the swollen under tongue soft squishy lump i have?

Floor of Mouth Lumps: Lumps under the tongue can have a multitude of causes. It could be anything from a plugged salivary gland to a cancerous tumor. You need to seek the immediate help of a specialist - preferably an Oral Surgeon. An infection in that area could also cause your throat to close and compromise your ability to even breathe. Please do not delay getting this checked out.

Sublingual gland!: It makes saliva when you are eating to aid digestion as well as swallowing!

Swelling?: Probably swelling if you had trauma or bit your tongue during your sleep. It could also be a mucocele which is a sac full of mucous that may need drainage and/or steroid injection to help prevent recurrence. If it's not painful or severe symptoms ok to give it a couple days to see if resolving. If not, or getting worse, or has been there a while get it checked out this week by your doctor.