You didn't ruin it. I'd say the biggest problem you'll have now is that when you begin to tiller the bow, you'll find that spot to be stiffer than the rest of the bow. And you'll have to either make it thinner in that spot (which I wouldn't recommend) or heat treat the other limb the same way to make it symmetrical, and possibly all working parts of the bow. That looks like osage to me, and it's not finished yet, so I think you can still finish it and back it, no problem.