I think i have an ulcer in my mouth. how do i get rid of this?

Depends on source: If the ulcer is traumatic in nature, it must be protected until healing can proceed. If the ulcer is infectious in nature (viral) or you have canker sores or if it is due to autoimmune issues, it just needs to heal on it's own. Some allergies can cause ulceration of oral tissues. If this is the cause, the offending substance must be identified and removed.