To think it’s spelt knob?

[Thinkingaboutsummer2020]

As in if you are calling someone a (k)nob - I see it without a k all the time. Is it slang like cum rather than come?

I'd say it's knob.

Regarding Spelt/Spelled. Apparently, Spelt is predominantly a UK spelling and Spelled is most commonly used in the US. (I wasn't certain, so checked Grammarly).

I think knob head looks weird.

If anything, it's knobhead. And no more weird than dickhead.

But nob head really is weird. Are you saying the person is the head of a noble? If not, what is it supposed to mean?