I’ve been reading many pages online about when it is best to cut nails
l’kavod Shabbos (for Ashkenazim). Now it’s Wed. night. Can I take a haircut?
You can have a haircut. The problem is only with nails because they look unkempt if cut 3 days before Shabbos.
O:CH 260 Mishnah Berurah 6.