If it's just blunted a little, you can use a sharpenning stone to grind a small amount of the spine away. I'll usually use a stone to grind the spine and then round it off towards both sides. When I have a knife with a "broken" tip, it usually means having the edge ground to the spine on a belt. But if it's just a little dull, I'd lighly grind the spine to the edge by hand. Also, sometimes I've found that by just running a stone at the right angle along the tip, on the flat sides of the knife, you can put a decent tip on it. Worst thing is that you end up removing some of the finish depending how much you have to do.