Pink bubble on the side of her mouth

For a few weeks, Samantha has had a corn kernel sized, pink bubble on the side of her mouth. I took her to the vet and she said that Samantha probably bit the side of her mouth and it will go away. It hasn't gone away yet. It's still basically the same size. It's on the outside of her mouth, basically on her lips.

Any thoughts?

Thanks.

Got a pic? My first thought could be an abcess if she also has a high temperature.