I had that problem once. I took a needle and thread, matching color, left a tail and slipped the needle through the knit loop on bottom and top, then next row, etc to close up hole. That way the knit would not come undone and the hole get bigger. When you get the hole sewn up, then you can tie off thread ends, but not too tight as to make a dent in the fabric. Hope this is clear enough to you. Easy to do, harder to put into words!