Or, don't touch your trussrod. If you can put very slight pressure behind the nut, and stop the buzz, you don't have enough break angle on that string.
Put on a new string, and use a few more windings. That will put the bottom of the string wrap down closer to the peg head, increasing the down angle of the G string. This should solve your problem.
I don't play MIM guitars, but if I remember right, they only have one strings tree right? On the E and B? If you really want to solve the problem for good, and not have to remember to extra wrap your G, just add a second tree on the G and D strings. That oughtta do it. If it already has a tree on the G and D strings, then a little adjustment might be in order. Worst case scenario, a new nut.
"99% of the world's lovers are not with their first choice. That's what makes the jukebox play." ~Willie Nelson