What can cause getting a canker sore and how can i get rid of it?

Herpes Virus: Almost everyone has this virus. Periodocally it erupts. It starts as a small blister, ruptures, and ends up as a whitish ulcer with a red border. It goes away in about a week. If you are a 5+/- year old, and this is your first episode, it is a little different. These are usually on attached keratinized tissue. They still end up the same way. Later episodes are as described above. They are not.

Canker Sores: are the most common oral lesions. Individual ulcers typically last 1-2 weeks. The cause is not known. The ulcers are usually self-limiting. Try to keep adequate oral hygiene as possible.