Is it mutar to squeeze out blackheads on Shabbos and Yom tov? I understand pimples are more problematic since blood may come out but this is not the case with blackheads. So are blackheads mutar to squeeze on Shabbos and Yom Tov or is there still a prohibition of making an opening (פתח) on Shabbos?
Yes, this is permitted. Blackheads are pores in the skin that have become clogged, so the opening is already there, they are being squeezed through the opening, so there is no issue of creating an opening on Shabbos.
See Shulchan Aruch O:C 328:28 and Mishna Brura 89-90.