The proverb must be expanded from its truncated form in order for us to understand it, but this is not hard given the total thought of the verse and the overall context. If the cleansing away of evil is accomplished by the administering of wounds or bruises, then these bruises are clearly delivered in discipline and correction to chastise the wayward.
God’s correction of his people also has a very good effect on them. ‘Now no chastening for the present seemeth to be joyous, but grievous: nevertheless afterward it yieldeth the peaceable fruit of righteousness unto them which are exercised thereby’ (Hebrews 12:11). In order to have this benefit, it must not be resented, but we must submit to it and accept that our heavenly Father does the right thing in correcting us and does it for our good. We must be willing to recognise our error and be prepared to alter our ways. We must see that God’s discipline leads to life if received in the right spirit and that God ultimately has our good at heart so that we welcome the wisdom that saw fit to chastise us in this way.