Roaring

[Eightball1978]

Hello I've been away from the forum for awhile,I suffered a head injury and I'm just getting back to my C10 addiction.(I tried a patch but it was mopar)
The other day I noticed a hint of a vibration and quiet roar,I assumed it was hanger bearing and greased it but wasnt it. So yesterday I drove the truck to try and figure it out but it stopped roaring and went straight to grinding,luckily I was just a block away. I frared the worst when I pulled the inspection plate the image is what I saw,I re tightened the pinion nut & the noise is gone. I don't know much about rear diffs should I replace the crush seal? Or Will that even help? Truck is a 1972 C10 Highlander edition, and the ration is (I'm guessing) is close to a 3:73. I've had probably a hundred car/trucks never seen this before.
I would appreciate any info. Thanks guyshttps://photos.app.goo.gl/n4LziVmh5qAySfGY8
BTW ive had the truck since 2015 and I think it has happened b4 cause the grooves look deeper than if it had just happened.