If you want to sound smart, you can refer to your finger, thumb, or toe as a digit. Each of the numbers from 0 to 9 is another kind of digit.
Although your pinkie toe may seem to be completely unrelated to the number three, each is a kind of digit. In fact, the practice of calling numbers digits comes from the digits on your hands — specifically, the habit of counting to ten on your fingers. The Latin root word digitus means "finger or toe," and English borrowed from this to mean "number."