You have a very pretty face, so a ring may detract from it a bit, in that it is a bit of a distraction. A small stud may be a little better. Would still involve a piercing, but would be a little less distracting. More of an enhancing what's there, if that makes sense.
People tend to focus on that part of your face that is pierced. When I talked to someone with an eyebrow piercing, I focused at his one eyebrow instead of his eyes when talking to him. So people will focus on your nose much more, I'm not sure if you'd like that.
That being said, I do think you have a nice nose shape and a nose stud could suit you.