Thy bruise is incurable - אנוש anush, desperate, not incurable; for the cure is promised in Jeremiah 30:17, I will restore health unto thee, and I will heal thee of thy wounds.
Albert Barnes
Notes on the Whole Bible
Incurable - Mortal, fatal.
Matthew Henry
Concise Bible Commentary
When God is against a people, who will be for them? Who can be for them, so as to do them any kindness? Incurable griefs are owing to incurable lusts. Yet, though the captives suffered justly, and could not help themselves, the Lord intended to appear for them, and to punish their oppressors; and he will still do so. But every effort to heal ourselves must prove fruitless, so long as we neglect the heavenly Advocate and sanctifying Spirit. The dealings of His grace with every true convert, and every returning backslider, are the same in effect as his proceedings to the Jews.
SDA Bible Commentary (limited)
Volume 1-7
12. Thy bruise is incurable. The reason God did not dare leave Judah “altogether unpunished” (see v.11) was that the people had by this time gone too far in their sins. Verses 12-15 describe Judah’s pitiable condition. Humanly speaking, there was no hope for her. However, God promised to heal her wounds (v.17).