When your horse steps on a nail or another sharp object, resist the temptation to pull it out right away. Doing so may actually make the situation worse.
Small puncture wounds on the sole of the hoof, such as those made by a nail, can quickly close. When that happens, the wound seems to have healed, but bacteria sealed inside the tract made by the nail can quickly multiply and travel to critical structures of the hoof, such as the coffin joint and bursa. A sad but all-too-common scenario is a horse who seems fine the day after stepping on a nail but two days later is severely lame with damage that cannot be reversed.
Call your veterinarian immediately if your horse has an object lodged in the sole of his hoof. If you can, hold the foot up to keep the horse from driving it further into the tissues. Your veterinarian may advise you to leave the object in place until she can get to the farm to take radiographs that will show the depth and direction of the penetration. This information will determine how aggressively the wound will need to be treated to ward off infection.
It’s also possible your veterinarian will tell you to remove the object, but she will still want you to note its entry point. And never assume the wound is shallow enough to manage on your own---there is no way to reliably judge this with the naked eye, and making the wrong call can have tragic consequences.