Some oral ulcers never seem to go away, with no signs (and symptoms) of healing. Of course, the stages may pass from a small bump to a small ulcer and subsequently to a bigger one, and possibly swelling. Then the swelling decreases as the ulcer gets even bigger, before it slowly heals thereafter.
There are all sorts of causes for your ulcer, from trauma, stress, dehydration, mouth breather to causes like SLE and inflammatory bowel disease. Treatment may varies, but I'm sure you know your usual treatment.
Being a typical mouth breather (and also because I seldom had enough fluids), I had all sorts of reason to have mouth ulcer. Various attempts had been made, from non-intervention (control sample), Listerine, salt water, drinking more fluids, ice-cream, watermelon frost to Bonjela. Sometimes this work, sometimes that work, sometimes all doesn't work. And that leads to frustration.
The worst ulcer progression would be those which swells and show no signs of it resolving as the ulcer enlarges. Those are usually the typical ones with the worst prognosis. It usually stays on for 1 week+ before it starts to resolve. So all in, the ulcer may stay for 2-3 weeks, being an annoyance for all sorts of oral activity.
And so I've found the most radical treatment that works for me. The ulcer usually resolves within 2-3 days totally, even if it's at its largest and swelling. The reasoning behind:
Step 1:
Apply salt on the ulcer. Yeah, salt on wound is sure painful. It stings too. But it burns through the whitish layer on top of the ulcer. Til it bleeds just a bit. Too profuse bleeding may indicate that you are overdoing it. Beware some may get high from the pain. If you can't stand the pain, try using salt water. The effect may differs depending on your salt concentration in the water.
Action: - reduces the swelling through osmotic effect + thins the protective whitish layer beneath to expose possible underlying infection
Step 2:
Use listerine. Gargle your mouth with the antiseptic. Kill off any underlying bacteria on the ulcer. Don't worry, at this stage, Listerine wouldn't hurt anymore. The salt had numb out all the possible pain. Make sure the oral ulcer is sterile.
Action: -Antiseptic
Step 3:
Apply a layer of watermelon frost just enough to cover the ulcer. It's rather cooling and it actually protects the ulcer just like how your whitish layer would do. Plus, it also has some osmotic effect to reduce any further swelling (though not as strong as your pure salt application).
Action:- protect ulcer base + mild anti-swelling effect.
With this, your ulcer will heal rapidly. Of course, remember to drink enough fluids, take enough vitamin C as well as other general preventive measures. You wouldn't want them to come back. :P
Disclaimer: This is not medically proven, just sharing some experience. Possibly just a cure to your normal (infected?) aphthous ulcer. The severity of pain may vary between people, so take your own risk should you attempt this method. n_n" Do see a doctor if you have recurrent mouth ulcers or if it is associated with any fever or rashes. You may have some sort of medical illness that requires medical attention. :P
PS: The author had just done this right before blogging on this.

