Yeah, they went out of their way to never show his face in the comics.....
right up until the fateful day that AOTC was "gifted" upon us all.
Then they had Boba Fett unmasked in the comics for the very first time, with Temuera's face but all scarred up. So the idea of him being scarred was around for a long time and it had nothing to do with Sarlacc damage.
Then again, I might be remembering incorrectly, but I'm fairly sure that scene was in the Tales of Star Wars anthology comic, and that was considered "non-canon." They'd have goofy stories every now and then, like a Yoda/Mace Windu parody of Pulp Fiction, or Indiana Jones finding the remains of Han Solo and Chewie. You know....FUN stuff that Disney doesn't like.
But there was a Boba Fett vs Darth Vader mini series that was IN continuity, and it showed the origin of the dent in Fett's helmet as a blaster bolt deflected back at Fett from Vader's lightsaber.
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Not sure what the current continuity claims is the source of the dent.