I have a small sore inside my cheek. the very tip of it looks red. it is very small, maybe a few centimeters.i can feel it with my tongue.

Centimeters?: Millimeters are small, centimeters are 10 times larger. See a dentist to evaluate. It could be something as minimal as an accidental cheek bite but needs to thoroughly evaluated and if necessary biopsied.

Few centimeters?: That's huge in the mouth! lesions in the mouth are usually measured in millimeters. Seek an evaluation by your dentist.