great on getting your colours right! getting colours spot on especially with flowers is hard to do when just starting out.
have to agree with big al here, don't leave your exif data off, it really does help folks with your photo when you want a critique.
as for composition it is not bad but it is what is in focus and what is not that gets the eye. my eye totally went for the front petal which is out of focus. if you want to get the whole flower then try bumping your apature up (that is your f-stops). i am going to assume that your apature was wide open when you took this shot so next time when you shoot flowers take several shots and with each shot bump the apature up. when you sit down to look at your photos you will start to see through the shots your whole flower start to come into focus with each shot you took. it is okay to have the front petal out of focus just make sure that it is not the focus point of your photo. have a look at
http://digital-photography-school.com/ they have some excellent tips and tutorials that will explain f-stops/depth of field.
as for getting lightroom, lightroom is an amazing program, very easy to use but it is pricey, same with photoshop elements or photoshop. what you would pay for lightroom, you could take that money and buy a decent flash because that onboard flash is in my opinion is horrible or if you got a flash then a nice tripod.
i made that mistake, i got lightroom when i got my nikon and about a month after having the camera i realized "hey this onboard flash is usless" but alas no money for a flash, so i had to wait and save for one. if you have everything you want and need then get lightroom but if you don't then i would hold off for a bit. your camera should have come with a 60 day trial of nx2 use it and if at the end of the trial you figure that you can't live without it then get it or get an adobe product. by the way nx2 is a great program and it is half the price of adobe photoshop. you might want to try gimp as well, it is no photoshop but it is free, not to hard to learn and it has more online tutorials than you can shake a stick at.