Hi!
Composition is good, and the background came out nicely. The flower is in focus where it probably needs to be. It looks good.
To improve it, you could probably do a couple things.
If you aimed the 430 at the flower, don't. Aim it up and away. If you're pointing somewhat down on the flower, you can actually turn the head of the 430 counterclockwise until it is backward. Do that and tilt it back toward you a bit to the 75° position (the first notch back from fully upright). This way you're bouncing the flash off of the ceiling. You should try other angles too to see if you get better lighting. This includes bouncing the light sideways off of the walls of the room.
You can bring out additional detail in post processing. How you do that will be based on what you use. DPP, Lightroom, Aperture, and other programs can help you do that. You want to see a little extra detail in the lower, outward stretching petals. For the upper part of the flower, you need to bring out much more detail.
Hope this helps! Experiment and see what you can do. Good luck and have fun!