If you haven't washed your shawls yet, I think you have a chance to fix it. Carefully pull out that duplicate thread. It looks like you accidentally repeated a pick while you were weaving. If you've done the same thing on the other shawl you should be able to do the same thing on both. However, leave yourself enough of that pick to carefully work both ends into your cloth so that they don't work their way out with use ;-) Cut the errant pick in the middle and gently ease it out on both sides and then use that thread to weave it back in so it's secure. It won't be as noticeable at the edges as it is in the centre.