My first post.
From what I can see in the photographs it appears that the blade is too hard. Possibly was not drawn back to correct temperature after hardening. Is this a laminated blade? I don't think it could be a cold shut, as someone suggested, as this can only occur when you are forge welding layers of metal into one piece and you have a spot where the weld fails.
This is not going to be a simple, quick easy fix. If this was my knife, I would remove the handle, reheat blade to a cherry red color and pack in vermiculite, wood ashes, or some type of medium to cool the blade as slowly as possible, may take more than one try. You need to get the entire blade back to a dead soft condition. When a file will readly cut any where on the blade, you can reprofile and regrind the blade. When the edge is ground, don't grind to a sharp edge. Leave the edge about the thickness of a dime. Sand blade to desired finish ,up to about 220 grit. Heat blade to nonmagnetic, about 1450 deg. F., quench in 150 deg. F., heat treat oil, this can be homemade (burnt motor oil & new oil mixture , etc.)
If this blade is 5160 (spring steel), after the above treatment it will be so hard that a NEW file will barely scratch it. This is too hard and will not make a good usable blade. This is the critical point in your heat treat. You must reheat the blade to the point where you are starting to take hardness out of the blade. The closer you heat it to 1450 deg., the softer it will be. My blades are heated to 365 deg. F., for one hour. Try the edge with a new file, if it will still not barely "grab"the cutting edge, raise your temperature another 25 deg. and try again. Continue doing this until you feel the file just beginning to cut the steel.
Now you can carefully, grind the edge to a sharp condition and test your blade on a good hard piece of wood to see how it holds up. If it is going to fail, you need to know now, before you put any more time into finishing the knife. Like I said, this is not going to be a simple 10 minute job to save this blade.
A simple regrind may or may not work. How much of the cutting edge is too hard? Was blade edge quenched or full length quenched? Is the tip too hard? I would not worry about answers to these questions and just start over again.
This is a very nice blade, beautiful fullers. I would try to save it.
I am one of the instructors at the ABS School. Passed Master Smith test in 1992. Taught numerous courses on Basic Forging, Damascus, and Handles and Guards. The above quickie explanation is exactly the way the ABS teaches beginning students heat treating. In my classes, we spend at least 2 days,trying to learn the basics of properly heat treating a blade. Not a simple task.
This is just my opinion, based on what I can see in the photos. This and a couple of bucks will get you a good hot cup of coffee at your nearest Starbucks.
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