You will probably need to replace the rocker and adjusting screw and nut . You will probably have to remove the rocker asm. any ways to get the adjusting screw out. I think it only comes out from the bottom (valve side) of the rocker because it it kind of flattened where the adjuster contacts the valve. You could always try to remove the good one right next to it to see if it can be removed from the top but I don't think you can. If you don't replace the rocker then you could try to re tap the threads if they aren't damaged too bad.