Looks really nice. I think you have done a good job. It doesn't look sharp though full sized... not sure if that is your export settings or slightly missed focus...
f/1.8 takes some practice... also might be worth checking your camera is focusing properly. I am pretty sure D7100 allows for camera/lens focus calibration.
It is wise to check the lens calibration and adjust if need be. The Nikon 50mm prime mated to my D700 required a minus 19 adjustment, pretty extreme. If your images are looking a bit soft, it could be due to a lens needing fine tuned.
As the others said; it's a nice image but slightly out of focus.
I don't know which focus method you used but if you use d9 or more, you run the risk the cam picks an area you rather have not. I had it happen quite a lot when practicing with wide open and find that using a single focal point targeted directly on the eye tends to give better results.