Job continues describing situations in which he would deserve God's punishment, but he is confident that they are not true. (See: [[rc://en/ta/man/translate/figs-hypo]])
Here "have hidden my sins" represents trying to keep people from knowing that he had sinned. Alternate translation: "If ... I have tried to keep my sins a secret" (See: [[rc://en/ta/man/translate/figs-metaphor]])
This represents trying to keep people from knowing that he is guilty. Alternate translation: "by hiding the evidence of my guilt inside my tunic" or "like one who hides the evidence of his guilt inside his tunic" (See: [[rc://en/ta/man/translate/figs-metaphor]])