You can squeeze, but not with your nails, you need a metal spot squeezer which is like a little stick with a small circle of metal at the top.
If you use them correctly they do not scar, they are used for professional facials at some places.
It is best if you open the pores a bit first with steam from having a hot bath and sweating (or a sauna/steamroom, but that is not practical for most people), then wash your skin with hot/warm water and a face scrub.
Do not try and squeeze red spots or any kind large lumpy spots with no proper head. You can only squeeze whiteheads and blackheads, you place the circle around them and slowly press down until the white stuff pops out, do not continue after that and you should not see any blood. You can feel a sort of pop and it all should come out in one go, after that, even if you think there is more gunk leave it alone for that day.
You need to keep the spot squeezer very clean, wash it with hot water between each squeeze during use and then disinfect it before and after each session with alcohol or something similar. Wash your face again afterwards with a moisturising face wash.
If you can be this disciplined about it is ok to squeeze, and can even be beneficial. The reason that the general advice to young people is always don’t squeeze is that most young people would not do all this properly and squeezing with dirty fingernails etc or even with a spot squeezer that you do not keep properly clean can cause scars sometimes and more often spread spots.