Allow me to jump-in, please ... a nifty fifty is a must for many many reasons!
It is relatively dirt-cheap! It is a very good lens for portrait (when coupled with a DX body, as is the case with the OP). It is great for low-light, unless someone has one of the f1.4? Can be used, very well, for great macro with extension tubes and / or reversing rings and these too can be had for relative cheap price.
It is a very versatile lens, that is well worth keeping "at home"; even if you don't use it for something specific, it will come in handy on that rainy day where you just go brain-dead and need a new angle!