Ok, you have to take the ball joint off to repair the threads. The first thing I would check is did someone put a metric nut in the new ball joint box?????? Next, fixing the threads: a threading die has been mentioned, the proper item is what they call a HEX RETHREADING DIE. This die does not cut threads but straightens them , same with the tap, if you already have threads, you don't want to cut new ones, that just removes metal that you need for proper torque. Also use a RETHREAD TAP, It will straighten the thread without removing metal and clean the hole of debree..