First off, it's never a good idea to leave a car running unattended (actually illegal in some states). Running without oil for 5 minutes has undoubtedly done some damage, but if you're lucky it may not have destroyed the motor. The ticking you hear is probably a lifter running dry.
Anyhow, what's done is done. I assume you had good pressure before and that you verified that you have oil reading on the dipstick now. Normally I'd start by verifying that the oil pressure gauge is working, but since you also have noise from the motor, I'd assume that's not the problem.
First thing I'd do is change the oil filter in case it has failed (see if a new filter restores pressure). If that doesn't help, you'll have to drop the oil pan and look inside.
You'll want to look at the pump and pump impeller shaft. It's unusual for a pump to fail suddenly but the impeller shaft could have snapped. If the shaft is broken, you'll probably find pieces in the bottom of the pan.
You'll also want to look closely at the main bearings (if you lost a bearing, you will get no oil up to the top of the motor).