HELP!!

So, this isn't exactly vintage (unless 80's? is vintage), but I hope ya'll don't mind because I really need some advice.  There is so much expertise in here, surely someone has a better way to fix this. I made this:

Well, I did make out of vintage navy polyester, which is not so fun to work with by the way.  Here is the finished work (without a bottom hem)

And here is the problem:

Me and my serger did not see eye to eye. I was trying to clean up the seams inside, but I don't have enough experience with the machine to know where to pivot to avoid the knife slicing right though and it did. And my mending looks awful partially because the unfortunate cut was through interfacing, facing and a seam. It's also in a terribly visible place right on the shoulder seam near the neck. *Sigh* Can anyone give me some advice to clean this up? If I have to remake this shirt, it will be the third time. I don't want to lose the time I put into it or to have wasted the fabric.

Thanks!

Carly