Don't cut it, I made that mistake and it just takes that much longer to grow out. When it gets long enough you can put the band further down the forehead, and it will catch some of the stray hairs, and there are various topknot gels that you can buy and are safe for dogs. I use Petsilk topknot gel, rub a little in your palm to soften, and dab it on the stray hairs. If you cut it you have to do it weekly, and I think it can make tearing worse, probably because there's always some short hair poking them in the eye.
PET Silk Top Knot Gel 4 oz (118ml) - Hold Fur Hair in Place for Dog Hair Bows | eBay