The "feed" part won't hurt anything, it's just fertilizer. But the "weed" part is a problem. Check the package and see what it is. If it's a pre-emergent, like Preen, you're probably OK. If it's a weed killer, like Round Up, then you could have trouble. Water, water, water! You want to try and dilute it as much as possible and get it to dissipate down through the soil away from the roots. You may see some peculiar or distorted growth as a result too but it should go away with some time.