Could be just in the lacquer - with his blessing (and if you’ve got the tools/are confident enough to do so...) take the neck off and look at the inside of the neck pocket.
If someone’s over tightened the screw nearest the crack - it can split the lacquer.
It it’s in the wood it’s a luthier ‘glue and clamp’ job.
if it’s just the lacquer, it’s a don’t bother unless you’re bothered, partial refinish...
looks nice overall though