Well, that's a toughy. My first thought would be to frog back to the error and do it right. After all, you saw the error, maybe someone else will too. And even if they don't, you will always know that you could have done a better job. But, if you're pretty sure nobody else is going to notice it, you could just make two decreases in inconspicuous places and go on from there.

It's not as scary as you might think to frog back to an error. Just thread a yarn needle with an appropriate length of contrasting yarn and weave through all the stitches on a row just prior to the error and unravel to that row and just slip the stitches back onto your needle(s).

I would rip it out to the correct number of stitches. You will be much happier with the end product.