PLEASE HELP! manual shift problem
 

Hi I have a 1995 pontiac sunfire with the 2.2. manual transmission, my problem is that the shifter cable that is attached to the shifter and then to the transmission keeps popping off on the transmission side, its like a socket on the shift cable and a metal knuckle/ball on the transmission side, anyone know how to fix? is it the knuckle or is it the shift cable? i need a cheap easy fix! thnaks