Very few people can get a word to slide in gracefully. Re-record the sentence or segment of narration that has natural breaks so the difference won't be as obvious.
We can't tell much from two seconds, but it sounds like you changed the face/microphone distance. That's rough to manage in post production. I have appeared briefly as two different people by just changing the microphone distance. It's a very serious sound change.
Again, two seconds isn't much, but it's a common new-user error to think they have to "live record" a correction like that. Make a protection copy of the "broken" work and announce the correction by just pressing record. Audacity should produce a second track with the correction on it. Tune which track to listen to with the SOLO and MUTE buttons.
Then use the Time Shift Tool (two sideways black arrows) to slide the corrected word into position, and the envelope tool to mute the old word at the right place. Audacity will smash both tracks together when you export.
http://manual.audacityteam.org/man/envelope_tool.html
This lets you add or subtract time, effects, and volume to the correction without affecting the main work. I would have increased the time between the existing and the correction, for example, which is relatively easy when they're two separate tracks.
And all that is why it's best to re-record the whole sentence or paragraph. It's far easier to hide minor changes like that.
Have you run into the ACX quality control services yet? We warn people not to record the Whole Book only to discover ACX won't accept your sound quality.
Koz