Alan, I had similar on my X-T2, it hit the deck from about 4ft, the lens hood took the brunt of the damage, camera appeared to work fine, but after a couple of weeks I noticed a 'sensor mark' similar to yours, several attempts to clena it resulted in no chnage, I then found that there was a small crack under the sensor glass. I suspect that somethingh flexed during the imapct, and this grew over time, like a crack in car windscreen.
It went to Fuji Service UK, who confirmed it and replaced the sensor.
Nothing compared to the damage on my GFX though
https://www.talkphotography.co.uk/threads/digital-medium-format-thread.699936/post-9015993