Ok, will buy the 18-55 if nothing else comes up, but I am more interested in macro and micro photography. I tried taking photos with my PnS through my microscope, but the results were not so good

So, anyone here ever done micro-photography?
Okay. But I'd like you to know this. Typical macro lenses have focal lengths around 90mm like Sujoy mentioned. That SEVERELY limits its paracticality for anything else. You will be able to get some pretty good protrait photos if you ask your subject to stand at just the right distance. To give you an idea of how it'll be think of your PnS PERMANENTLY set to 5x zoom and walking around with it taking photos. How much will you like your PnS if you cant change its zoom to anything except 5x ? Thats roughly how using a 90mm Macro would feel like.
Thats also the reason why I harp so much for the 18-55 IS variants. The canon one (and so I guess even the Nikon one) can focus as close as [25 cm - length of lens in cm] centimeters. It isnt macro, but its pretty good for a beginner. And surely vastly more versatile than a 90mm macro. I'm not dissuading you from buying a macro, but ~20k is a serious investment and you should be aware of what you are jumping into. If macro is so important to you that you are willing to buy a lens thats pretty much useless anywhere else, then sure, you'll love the dedicated macros.
ANother option would be the 18-200mm lenses. Good ones cost ~27k (I guess) and they are very versatile. They cover a decent zoom range (near wideangle to near telephoto) and though they can be bested by dedicated lens at either of the 18mm and 200mm ends, they are probably your best bet for your particular use-case. Get a D3100 + Sigma 18-200 if you think thats fine. That should be ~50k I guess.