Assuming the eraser side is still in working order, it is possible using a soldering gun to solder off the working end and resolder it onto the side you normally draw with. However, you have to be quick while soldering or you will fry the microchip(like I did one time) Or, if you use SAI, you can use either end of the pen for drawing.
But the best option is to just get a new pen. Those options are best for a quick-same-day type fix.
At least if the part you're talking of is what I think it is.