try shrugging with both...
you are probably nitpicking.
my left chest is bigger than my right chest,
my right arm is bigger than my left arm
my left calf is bigger than my right calf
my right thigh is bigger than my left thigh
my left delt is bigger/more devloped than my right delt
and some days my left lat is bigger, and other days my right lat is....
just keep lifting hard and with good form, and things will work itself out over time