2000 Dodge Truck Oil pressure gauge

I noticed suddenly that the oil pressure gauge dropped tp near nothing at idle (the alert came on), but when I revved it up it came back up to the 40+ psi range. This happened twice in a row. I also noticed at the same time suddenly there was a slight knock in the engine (like the sound of too low octane gas) at higher speed, but that was sporadic. I drove the truck home and parked it. It's a third vehicle I use just for hauling. I'm always afraid of screwing up the engine when the oil pressure goes to to nothing. Should I have it towed to a shop, or is it safe to drive it there (about eight miles)? Do you think it's anything other than possibly replacing the oil pump, which may be bad?