‘Back in the days’ meaning a time in one’s life looked back upon with great fondness. Usually invokes a memory of a particularly memorable or traumatic incident. Tone is describing a time before you even heard the term you use now.

Back when the only chance to talk to people was when you were at school.

Kids feel that there’s no reason for them to care about others since they live simple lives, after all ignorance is bliss for a reason.

Kids live life without a care in the world and don’t take school seriously; they don’t set goals for themselves or learn any necessary skills to live in the world, which leaves them wandering around not knowing who or what to believe in.

Damn son! They start so young

You’ll regret the decisions you made when you were younger.

This is an old expression meaning that you’re depressed or unhappy about something.

What’s in my head
I can’t see

(SPOILER ALERT) This could be referencing what happens to Kno later in his verse since he describes being shot from a shotgun and realizes that the blast hit his face as well as his body.

Also a confirmed case of Kno getting his David Bowie on.

Kno remembers he left his cell phone in his pocket and grabs it to try and piece together what happened to him.

Kno is in pain from being shot as he tries to walk to the front lobby of the hospital, but realizes the shotgun blast hit him in the face as well and now believes he’s unrecognizable to those who know him since he can’t seem to find anyone.