If you are serious about your knives then you'll probably have some sharpening rods on hand, or a stone or two. Absolutely don't file the edges...use a stone on them. It will take you a while. Concentrate on the edge...NOT the nick. The nick means nothing if you have a nice edge on the blades. Lansky is a pretty good source for knife sharpening goods. If you don't already have such things, you're gonna spend a lot more money on them than just going out and buying a new cutter.
I don't spend a lotta money on cutters. To me, they are just a throwaway item...when they get dull, toss and buy another. I'm not gonna spend a hundred bux on a cutter just to watch it get dull like a $4.95 cheapie and then throw it away. To my way of thinking, if I'm gonna spend a hundred bux, the manufacturer needs to keep the concept of sharpening the blade easily and regularly by the consumer in their game plan. Doesn't seem like they do.
Just sayin'...