Quit eating sours for now. The sting will go away after a while, but try not to eat anything acidic. Drink water or milk, and remember-don't eat too many sours at a time. It will always end like this. If you haven't already noticed, it will also be hard to taste other foods.
It's an ulcer from the ascorbic acid powder on the candy, the ingredient that makes them sour. Sometimes sucking on a milk of magnesia tablet might work. Other than that avoid high acidic foods and eat dairy products. It will go away it's own. It could be hours or a day or 2 depending on how many you ate.