Oil Change

Hey, I'm a new driver, and being the smart person that I am.I have been driving with barely any oil for 2-4 weeks. I know it was that long because that is when my red "(!)(P)" light switched on. My dipstick had blackish coloured oil on it (assuming it was burnt), so I filled it to it's requirement. I tested my car for a couple minutes, and the strange noises started to go away, but the car still didn't seem right (driving wise). I have a 92 Honda Accord, and it was "jolting" occasionly when I shifted (as if I was low on gas), but I just filled it up. So my question is. Have I damaged the pistons? Sparkplugs? And how long will it take for the oil to run through the engine? (When will the red light turn off?)