Generally low-end DSLRs are sold with a kit lens which is of very poor quality. The AF-S 18-55mm F/3.5-5.6 VR is probably what came with your camera and definitely falls into that category.
What you are looking for is a Macro lens which Nikon labels Micro. Price varies but there are plenty of rather affordable ones for Nikon F-mount. Nikon makes a surprisingly cheap DX 40mm F/2.8 which produces better image-quality that what you have and is quite sufficient for online use. There is also a 60mm F/2.8G and DX 85mm F/3.5G VR which cost the same price but are better optically than the 40mm. Also because they both have a longer focal-length, you have more working distance between the camera and subject. This is matters as with the 40mm you have to be really careful not to cast a shadow on the subject.
Third party makers like Tokina and Simga make fully compatible macro lenses at a similar price. There are a few cheaper brands that make manual lenses but those are probably best avoided for a beginner.