Canker sore.!???help me it bothers me ALOT!?

ive had this wart or canker sore.?? in my mouth and it bothers me alot i cant eat well..and i have a mild pain..i brush twice a day and floss once a day.what are the possible causes for this.?what can i do about it.or does it go away itself.?help me out a bit.thanks.*