Jim my former son in law did the same thing to mine (burnt the front pan bad) a couple of years ago. Your pan may be warped now but that doesn't seem to affect the way it boils. If letting the sap sit in it and vinigar doesn't clean the burnt stuff off the pan cleaner acid works real well. I don't like to let the sap soak in my pans, the mold and sour sap smell are hard to get rid of.
Sweetwoodmaple the season never ends around my place. The boiling and making syrup does but the cleaning and canning take up a quite a bit of time not to mention the tubing maintainance and wood cutting etc.
Russ