The code that you pulled will stay in the memory of the car for the next 20 key/ignition cycles (I think). Stays there so that the service garage can at least look back for a short time to see what the car has been doing. This is normal, and if you check it again in a week or two the code will just be gone...
As far as the 'check engine' light goes, it will come on whenever a service code gets registered in the system. It will stay illuminated for the next number of key/ignition cycles at which time it will turn off if the problem is no longer a problem.
Also be aware that the 'check engine' light can illuminate and stay on, or blink. If it's blinking, stop the car & engine immediately as this indicates a critical problem that further running make much worse. If it just lights and stays lit, it's a problem that you should either take it in for and they'll scan the codes for the problem, or as you've done already, check the codes yourself.
With your issue I'd say that the low oil likely caused this code. The EGR (Exhaust Gas Recirculation) valve is part of a system that controls harmful emissions of the engine, as well as ping control, among other things. Without looking in the manual I couldn't tell you where it's exactly located at on your engine, but in the old days it was right next to the air cleaner, mounted right to the top of the engine - an easy replacement if needed. In these newer days, this valve has a sensor mounted on the top that detects its position and reports it back to the car computer. On your car it probably was stuck in a high position as a result of the greatly diminished oil supply. Oil pressure has everything to do with the proper operation of this and many other systems on the car. Once you got oil back in the engine and the computer monitored all the sensors for a while again it turned off your 'check engine' light.
P.S. - here's a pretty good article on the subject:
Lots more with a google search: