How can I remedy a slight bump underneath my new hardwood floor?
Nailed down hardwood board strips can be removed (destructively) to allow access to the offending sub-floor.

It involves carefully cutting out the piece with a circular saw and an oscillating saw.  

Replacing the piece involves glueing down the same length piece. You have to cutoff the bottom half the groove side to allow the replacement to drop in.

Hopefully your flooring was  prefinished, which makes matching a snap