If I feel a canker sore coming on, I put a wad of chopped sauerkraut on the area, hold it there for a minute, then chew and swallow. I do this three or four times a day for two to three days.
Trauma to the mouth from sharp food can trigger a canker sore (aphthous ulcer). So can immune suppression or a deficiency of folic acid, vitamin B-12 and iron. A 1930s remedy recommended swishing sauerkraut juice in the mouth several times a day. Perhaps the bacteria that ferment cabbage into sauerkraut provide helpful nutrients.
A 2009 study demonstrated improvement in canker sores from 1,000 micrograms of vitamin B-12 daily (Journal of the American Board of Family Medicine).
I get nosebleeds when the furnace runs a lot in the winter. My doctor recommended Vaseline in my nose to keep it moistened.