So basically, the eye scar is a scar from Hal before Jestar got defeated, he got headphones (ofc) and then kinda joined the team, another thing is if Jestar gets close to Hal, Nauti doesn't want Hal to use some power so Nauti slaps Jestar away, but since he has spikes on his hands, it leaves a blood cut, they do heal but Jestar gets close to Hal often. But not intentionally mostly.

yeah bb got hurt