I have a 2000 jeep cherokee classic with the 4.0 and I replaced the oil pressure sensor but I still have low pressure at idle. What else could this be? Should I be worried?

 

Maybe.
What exactly is the oil pressure?
And how warm is the engine?
Any idea what it reads at a hot idle?
Did you give the wiring a good once over?
But before you get yourself all worked up you should check the oil pressure with a mechanical gauge.
This will require taking out the sensor.
Also clean out the hole the sensor goes in.
Maybe a pipe cleaner.
Go from there.
Last thing is where did you buy the oil pressure sensor.

 

The engine was around 210 where it normally is and the pressure was at 10 it was a drualast sensor from auto zone

 

10 PSI at a very hot idle?
Also skeptical of the Auto Zone sensor.

 

I will bet it is not the sensor if both read the same at hot idle. It could be the gauge in the instrument panel or related connections so the mechanical gauge check really should be done as Ralph recommended.

Miles on engine? Coolant usage? History of overheating? Hot oil pressure on highway at 2000 RPM?. As you probably know the 2000 and 2001 XJ's used a head casting that was prone to cracking especially if overheated. This often allows coolant to contaminate the oil and that can result in accelerated bearing wear. Excessive bearing clearances will drop oil pressure.

Verify oil pressure and report back the results. I would not drive it much until the issue is identified.