Note: this cheat works for pattern stitches that have a nice easy repeat. Here, I'm actually using Lucy's ripple pattern which uses four stitches then either two decreases or two increases, depending on whether you're at a peak or a trough. The pattern row ends with one increase, so as you can see, I have a few too many stitches.
So, to fix this wee problem, start with the knot.
You need to unknot it.
Do it gently so as not to pull the rest of the chain tight and you'll have a sort of loop on one side and the tail on the other. Keep pulling the loop until the tail comes all the way through.
Rinse and repeat until all the spare stitches have gone.
Personally, I like put the knot back. You could, I guess, just sew in the end and pretend it never happened, but it you want to put a border around your work, you'll need a little more stability in that corner stitch. To do this, start to pull the tail through the loop as if you're undoing it.
You don't need to pull it far, this much should be enough.
Pass the end of the tail through the loop to make a new knot.
Ta-daa! Nobody will ever know.