Do you have a floor jack or any way to jack the vehicle up? Because that's going to help you out a lot if you can. So....if you CAN jack it up:
Jack up the problem side (if you are unsure of which side is giving you trouble, apply the following process to each side). Turn the steering wheel to full lock (either direction) and attempt to spin the wheel in the air. If you feel some resistance, along with grinding/popping/other noises, you'll need to replace the U-joint.
To be doubly sure it's the U-joint, turn the steering wheel so the wheels are pointed straight. Now try turning the wheel in the air again, listening for grinding/resistance. Try grabbing each side of the tire and moving the wheel back and forth. If there is play in the wheel and noises when you turn it, then you'll need to replace your wheel bearing.
I'm not a mechanic, so what I have listed here is not science, but it's worked pretty well for me over the years.
From your description in this thread, I would say you're probably going to be replacing the U-joint on the problem side. U-joints are probably the most common repair I have run across with Cherokees, they go out all the time on these things. The U-joint costs just under 25 bucks at napa. Be sure you put extra grease in the caps before installation, it'll help prolong life. If you need direction as far as taking the hub off and axle out, and how to pound the old U-joint out, let us know. Good luck!