A known damaged U-joint should be repaired promptly. Continued driving can allow wear or binding to worsen, and a joint failure can damage the driveshaft and surrounding components or interrupt power to the wheels.
There is no dependable safe driving distance based only on a noise description. The severity of the wear must be assessed.
If you notice strong vibration, heavy clunking, or evidence that a driveshaft is loose, stop driving and arrange assistance. Contact Certified Transmission in Council Bluffs to discuss inspection and transportation options.