Infection usually becomes evident 24 hours after injury. You also should consider seeing your doctor if the cut is too large or deep for you to keep the edges together. Keeping the edges of the wound together helps keep the dirt out and decreases scaring.
Stitches provide the best insurance for holding the edges together, but they can cause scaring, too.
Because of this, your doctor may suggest using butterfly bandages. The wound's edges won't come together or the wound is very irregular and there are flaps of tissue. Date of last tetanus shot is unknown, or wound is not small and clean and your last tetanus shot was more than five years ago. The wound is very dirty or contains foreign material that is not easily washed away. There is weakness or numbness below the injury.