Acne scars can happen without infection. I have a few pit type scars from spots I did not pick and did not get infected. OTOH I don’t tend to get scars from zits I pop. I get lots of zits, not many scars.
Some times if you don’t pop the zit, the center of it keratinizes leaving a hard mass that is not reabsorded. This can stretch the pore and cause it it for scar tissue around the strethced pore. The pore is no longer exerting much sidwiays force to hold the hard core in and if the surface skin wears off, it can fall out, leaving a pit.
Zits are fun.