I'd suggest a visit to a good gun shop. Talk to them, handle some guns, and get a feel. Look at holsters, see how they feel, and how practical they really are. For example, I don't like inside-the-waistband holsters. Not practical for someone built like me, with some extra weight. And I just find them uncomfortable. I prefer pancake, or paddles if I want it to be more removable.
I carry a Glock 27 off-duty and when I need a more concealable gun than my duty Glock 22. Part of that is agency regs, part of that is convenience and a desire to maintain a consistent platform. It is small for my hand, even with a grip extender. (I don't like the extenders that allow extra rounds; to do so, they adjust the spring slightly, and that's just an opportunity in my mind for a mechanical failure. The extra 1 or 2 rounds ain't worth it, in my book. Other folks feel diffferently...) But if concealment is a bigger issue -- there are other guns out there that are better, including revolvers. In fact, if you're not going to practice regularly with it, including malfunction drills, I'd strongly suggest considering a revolver. Less to go wrong... and often more concealable.
I'm not personally familiar with the Nano at all...
Oh -- I'm not a fan of women carrying guns in purses, or men carrying them in backpacks. I want my gun on my person, under my control, not in something that can be removed, dropped, left in the car for "just a sec" while you run in somewhere...