Ouch ! I know how frustrating that kind of a burn is. The bad news is the enamel may well have cracked, sometimes -if it's not too bad- continued use is possible, if none of the enamel has cracked off. See what happens after boiling 2-3 pots of water & discarding them - I'd continue using, but not leave water standing for any length of time.
I use just plain ordinary baking soda to remove burn residue - cool the 'pot' - sprinkle generously with baking soda - add a small amt of cold water - slowly bring to a boil - cool - and more often than not blackened material will lift off fairly easily - scoure gently with regular kitchen brush occasionally a second go is needed (son learning to cook on his own-he's grown-up) Baking soda & a few drops of water also make a good scrub for the outside to remove smoke/soot residue. Plain old bottled lemon or lime juice work well to remove spots or stains on cookware.