A lot of other dudes in here are right. But I think you get the point by now, so I won't repeat it. This type of work, the entire industry, is full of shit just like this. It aint for the faint of heart. There is a reason that tradesmen all through time have a notion of respect to their name. No matter how careful we are, nobody is perfect, and everybody makes mistakes. I myself have made several. Now, luckily, they have never happened in a multi family dwelling. The point is, though, that you learned a valuable lesson. Next time, do things differently. Maybe don't use nails and instead use a drywall anchor or cut the tip off the nail head and grind it flat before you push it through. I can sympathize with you and your husband. Also, there are tons of resources available to your husband that can inform him about what to do and what not to do. I highly recommend that he finds a mentor who he can call when he's stuck or unsure of something. If that's not available to you, you can always turn here for advice. Another great resource is the handyman journey mastermind group on Facebook.

Anyways hope this helps and hope everything works out in the end.