If you camera still works normally, I doubt if you damaged anything. Most of the focusing motors (AFS) in the lenses have a clutch that prevents any damage. Was your camera turned off when you removed the lens? You should always turn off the camera before removing any parts. If it wasn't turned off, you might have heard the focusing motor working against any supplied voltage to the lens. It should still be OK, but take the proper precautions before removing the lens - turn off the camera, work in a clean and preferably in an environment with clean air and minimum air circulation - do this in an attempt to keep the sensor free of dust.
Your existing lens is a very capable optic. Another lens that is a nice lens for subjects that are not very far away is the 35mm f/1.8 AFS DX lens. You might find this lens a surprise for your portrait and maybe dog pictures. If you set your current lens to 35mm you will see the coverage that the 35mm f/1.8 lens provides. The advantage of a second lens with this angle of coverage is 1) a faster lens that lets you take images in lower light and is a bit easier to see through for focusing and composition in lower light and 2) very good image quality at wider apertures with the wider aperture giving you a bit smoother out of focus background, something that creates a three dimensional effect in your images - separating your subjects from the background. If you set you existing zoom to 35mm and don't find that the image is interesting or see an obvious application - just move on .
Roger It is still ISO, aperture and shutter speed, right? "Nikonians membership - My most important photographic investment."