The language in this verse is reminiscent of the time of the exodus. As once the Lord smote Pharaoh with plagues, so he will strike Egypt with blows in the messianic time (the same verb is used in both cases). Egypt will be treated as a true child of God. The blows will not destroy them but will lead to healing and a closer relationship with God.
22 And the LORD will strike Egypt, striking and healing, and they will return to the LORD, and he will listen to their pleas for mercy and heal them.