Explain to the child that each face is for a person who feels happy because he has no pain (hurt) or sad because he has some or a lot of pain.

Face 0 is very happy because he doesn't hurt at all.
Face 1 hurts just a little bit
Face 2 hurts a little more.
Face 3 hurts even more.
Face 4 hurts a whole lot more.
Face 5 hurts as much as you can imagine, although you do not have to be crying to feel this bad.

Ask the child to choose the face that best describes how he/she is feeling.