The first step to treating any lip injury is to stop bleeding by applying pressure, according to the University of Rochester Medical Center. Because the lips have a large blood supply, lip cuts tend to bleed excessively. If the injury is on the outside of the lip, clean the area well, and apply an antiseptic spray or lotion. For cuts inside the lip, simply rinse the mouth to remove any particles.
Apart from the problem of additional bleeding, the rich blood supply in the lips enables them to heal quite fast when injured, explains the University of Rochester Medical Center. Most superficial cuts that are smaller than half an inch in length heal easily on their own simply by keeping the area clean. Suck on ice to prevent swelling and avoiding blowing on the wound.
In the case of a deeper wound or one that does not stop bleeding within 10 minutes, seek the help of a physician to ensure the lip heals properly, according to Colgate. Puncture wounds and deep cuts require medical attention, as do lip wounds caused by animals or rusty objects. As with any wound, see a doctor if there are signs of infection. In some cases, lip wounds inside the mouth require an antibiotic to prevent infection.