I have a huge lump under my tongue on my gums?

Hi I want to thanks everyone that response to my question in advance. I have a huge lump about as big around as your pinkie finger on the side of my gums under my tongue. It doesn't hurt and I have no teeth I wear dentures but haven't worn them for a while because of this lump I can't get them in. Any idea what it could be? Thank You for your ideas.