I figured out a way to do this that is a bit complicated and annoying, but it worked. It's going to take a lot of cheats, especially is your sim as certain levels of skills and relationships built up.
So first you're going to have to get your family into the CAS menu during normal gameplay.
Then, you're going to have to make sure that you save your household to your gallery, this is important.
Next go to the gallery and take the household that you just saved and add it to it to your current household. It will download all of the sims in your household already. Be sure to delete the sims that you do not need doubles of.
Once the only duplicates you have are the sim you need to fix, delete the original sim (the messed up one). You can do this by clicking on the sim like you are about to edit them and click the x that will appear over their head icon.
After that you can leave CAS and everything will look the same. Your skills, aspiration accomplishment, and public image should all still be the same. The only things that will reset are your career and relationships.
Hopefully this helped!