Ok, First off, If theres no noise in the engine, you can stop worrying.
Whew, feel better now?
The 6 cyl jeeps are notorious for bad oil pressure switches (the switch that tells the gauge what to read). I would bet that this is your problem. Besides the switches going bad on their own, sometimes careless techs changing your oil filter, will mistakenly crack the switch causing the same symptom.
The course of action for this is simple, bring it to a tech and have him check first to see if the switch was damaged during your last filter change, if it was, I'd bring it back to where it was changed and have them replace it without charge.
If the switch is intact, the tech will hook up his own test gauge to see what the true oil pressure of the vehicle is. He'll remove the switch and insert his tool and get a reading.
Now, chances are your switch is bad, and if it is, he'll replace it on the spot while the bad one is out (this is relatively cheap, I get under $100 for the job, inc. labor).
If by some chance he finds that the pressure is high (unlikely) he'll check to make sure the oil filter isn't defective, or that there's no blockage anywhere.
%95 chance the switch is bad.