Do you mean dull tip as in the blade edge toward the tip is not sharp, or that the tip, which should be pointed, is rounded off?
If the former, just sharpen the knife and be sure you're getting the edge at the tip of the blade.
If the latter, you can just wait it out and sharpen the knife "correctly" from now on. Over time, it will be corrected. Otherwise, you can remove some metal from the spine of the blade to restore the point. Do this with a belt sander or bench grinder, but be very careful not to mess things up (and if things get messed up, it will happen FAST.)