Can panadol (acetaminophen) mask the fact that one has a dry socket?

Not generally: Panadol (acetaminophen, paracetamol) is effective for mild pain, but would usually not be sufficient to control the pain of dry socket. Your question is more of academic than practical importance, because treatment of dry socket is limited to pain management, so "masking" of the pain of dry socket is a desirable goal. Dry socket requires no additional treatment other than waiting for resolution.