The Lion was also puzzled to know what was wrong.

But the Scarecrow seized the oil-can from Dorothy's basket and oiled the Woodman's jaws, so that after a few moments he could talk as well as before.
"This will serve me a lesson," said he, "to look where I step.

For if I should kill another bug or beetle I should surely cry again, and crying rusts my jaws so that I cannot speak." Thereafter he walked very carefully, with his eyes on the road, and when he saw a tiny ant toiling by he would step over it, so as not to harm it.

The Tin Woodman knew very well he had no heart, and therefore he took great care never to be cruel or unkind to anything.
"You people with hearts," he said, "have something to guide you, and need never do wrong; but I have no heart, and so I must be very careful.

When Oz gives me a heart of course I needn't mind so much.".