What can I do with badly cooked honeycomb?
It might be possible to dissolve the candy, and then boil it down again, foaming it with fresh baking soda when it hits the proper stage.  The thing is, the candy has already got the full level of baking soda reactants (either sodium carbonate or sodium oxide) from from the first cooking, which may contribute to some off flavors.

Instead, if it is enjoyable as is, I would suggest just eating it as a toffee like candy.

Otherwise, chalk it up to experience and watch the temperature more closely next time.