Taking off single-digit HP doesn't mean shit. There's a reason Kaido hyped CoC attacks and why their attacks weren't working before. And this is not even mentioning how fast Kaido regenerates. So no, that shallow damage was almost about negligible and most, if not all of the other damage was regenerated because none of the other attacks left any kind of scar. Like, even after the Scabbards fight, Kaido was COMPLETELY clean by the time the SNs came on the roof to fight him. Everything regenerated.
The thing is, if they were actually doing any kind of damage other than it being negligible, they would at least leave a minor scar. But what happened was that Kaido was completely clean after their fight. Like not even a scar after some time, it just got regenerated. Now, that regeneration might be taking away his stamina but even that won't really mean anything considering that top tiers like Kaido have the ability to fight for days at length.
Zoro and Yamato are the only ones whose damage really stayed with him for some time due to CoC. Even the Asura attack from Zoro healed up in a chapter or 2 and turned into a scar, probably depleting his strength a little. But the fact that it has already healed and turned into a scar speaks a lot about his regenerative abilities. Even the damage by Yamato's CoC imbued Thunder Bagua mostly healed after a few panels. But they were probably still doing some internal damage so that mostly took away some of Kaido's HP.
Kaido's durability is at a very different level when compared to WB, even more so when we're talking about sick and old WB. You don't need CoC to damage him and almost all attacks on him mostly stayed instead of regenerating like Kaido. The wound by Squard stayed for a considerable time with WB but if that had been Kaido, it would've healed almost immediately, much like the stab wounds from the Scabbards.