The canker sores are different from cold sores, they are small in size and thin ulcers, which appears in the mouth like on the tongue, soft palate or inside your cheeks. In the presence of the canker sore, eating and talking becomes painful. These canker sores are of two types, namely, simple and complex canker sores. The simple canker sores appear 3-4 a year and sustain up to a week. The complex canker sores are not common, but occur most often in the people who previously had them. The symptoms of canker sores are painful sores inside the mouth and a burning and tingling sensation before the sores appears.