I would do it over if you want it to look nice. I agree with Jan, I never back stitch anything. If I see a pattern that says to do that, I just ignore it and sew it the "better" way.
Here is a link to some very good information about seaming in different situations. She covers bound off shoulder seams, and side seams. Read chapters 17, 18, 19 and 21 to get the full scoop on the seams. LINK
I'm not sure how your issue with the trim you did will play into all this. I hope it works out well for you.