Swollen white colored ulcer in far top left corner of mouth inbetween gum wall and teeth. what is wrong with me?

Hard to tell: Could be a canker sore, could be an infection from your tooth. You need to be examined to know for sure. Call your dentist.

Your OK: Without seeing you, you probably have an apthous ulcer, sometimes developing from trauma, a virus, certain foods (spicy). These can be clusters or single, causing alot of localized pain, sometimes making the entire mouth hurt. These are self limiting & go away without any help in 7-10 days. If you need peace of mind have your dentist take a quick look.