Just double checked. Looks like beta-canon from the novels. Interestingly, according to Memory Alpha, the first episode or two with Bajorans in TNG had all the male Bajorans wear the earring on the right and all the female Bajorans wear it on the left, but right ears for both sexes became standard pretty early on. The only other named character that wears it on the left is Lt Mura in PIC.