Answer:
It means psychological wounds that Ahab possesses because of his obsession with the whale.
Step-by-step explanation:
This book presents a metaphor that all the power and wisdom that man believes to possess are illusory; that in the end he will always be subject to the whims of nature, which at one moment can favor him with wealth and prosperity, and then crush him like an insect without warning or remorse.
As a representation of man's impotence in the face of nature, we have Captain Ahab who is an old man who feeds a giant obsession and hatred for the giant whale, this caused the captain to lose one leg and terrible "dents" on his face. Since then Ahab has gone in search of this monster swearing cruel death.