There's a bump in my mouth. It's white in the middle and red around the edges. What do I do?

I had something like that about a week ago it took alot to get rid of and it hurts its infected and it swelled i used listerine for a about three days and it went away gargle with it and rinse and swish for about 1 minute you can do this two times a day listerine kills germs and that is how it got infected with to begin with but it should go away after two or three days.