Does anyone know what these are? I occasionally feel a bump in my mouth and always wonder what it is, and today I finally took a photo and have no idea what I'm looking at! They come and go, and as you'll see from the second pic, which I took last week I think as I had sore teeth, there is a vague mark where they are. I don't think they're ulcers as they're not painful. The swelling normally lasts for about a day or so and then just goes!