In Proverbs 20:30, it reads, "The blueness of a wound cleanseth away evil: so [do] stripes the inward parts of the belly." What does blueness mean?
This is the older way of say "bruise." We still keep memory of it when we say a person was beaten black and blue. Bruises look ugly and they hurt, but the body bruises in order to heal damage. We have to put up with the discomfort for a while in order to get better in the long run.
What is being pointed out that we so often avoid pain in ourselves and others. We don't like to be sick with grief. Yet those hard times of pain and grief are needed to get many people out of their sins and on the right track. Recall, for instance, the story of the prodigal son. Protecting someone from all pain or consequences of their actions can actually be harmful to them in the long run. Think of how many spoiled brats are raised because their parents constantly rescued them from their mistakes. They would have turned out better if they were allowed to experience the pain of their sins so that they would remember to avoid them in the future.