Looks like stem rot. Hard to recover…
Best chance clean a razor, scrape lightly until most of the grey area is removed. You will expose the light green underneath. Use peroxide to clean the area, and use a fungicide. Repeat with fungicide every few days…
it might not work, or it might save the plant. Did this with my last run.
Without treatment it will continue to shrivel and the plant will fall over, and inevitably die. Sorry to say. My ILGM Banana Kush was very susceptible to this and it happened with a few of them if I’m remembering right.
Edit
I also use natural honey on the wound before spraying the fungicide.
This is just my experience, look forward to the other responders.