I'm the same as the pp's. Have I heard somewhere that the left side of our bodies are slightly bigger than the right? Well, I know mine is, including the breasts. With my first pregnancy, both my breasts leaked from about week 25 or so onward, but the left always leaked quite a bit more. It ended up being the side that gave much more milk as well, even though (like you), I have more of a flat nipple on that breast.
So yes, I do think it's normal. And I don't think your inverted nipple will hinder your milk production at all. Although you may have more trouble getting your baby latched onto that side (I know I had more trouble getting ds latched onto my "flat nippled" breast), but there are things that can be done about that, so I wouldn't worry about it.