Dog wounds are often deceptive---what looks like a small, unassuming injury on the outside, can actually be quite deep and extensive underneath. If your dog has suffered a wound, whether from a dog bite or a lacerating foreign object, it may heal on its own; however, there is a very good chance that it will become infected and require treatment from a veterinarian. There are a few symptoms your dog---and the wound---will display if it needs to be addressed by a doctor.
Observe any bleeding. While most wounds will bleed a bit, they will typically resolve with only a small amount of blood loss. However, if the wound will not stop bleeding or it appears to be releasing a large amount of blood, rush your dog to the veterinarian, as it may be a life-threatening situation.
Note any swelling around the wound. Swelling can occur below the wound, as fluids will travel to a low area. The fluid may be pus and the swelling can either feel hard or soft. If any swelling occurs, you should have a vet take a look at it, since it is probably infected.
Smell for any odor. The presence of a foul scent is a strong indicator that the wound is infected and requires antibiotics and perhaps further treatment, such as skin debridement and thorough cleaning.
Look at the wound and around it for any redness. This change in color of the skin over or around the wound is usually a sign of infection. In addition, if the wound or skin around it feels warm to the touch, the dog should see a veterinarian for infection treatment.
Measure the length of the wound. If the wound is over ½-inch long, it will likely require sutures, which should be placed by a veterinarian.
Watch your dog for any behavioral changes. If the canine displays a change in its appetite, seems depressed or lethargic, has an elevated temperature or a decrease in its appetite, it should be examined by a vet. Not only is an infected wound possible, but the dog could be anemic and at risk for becoming septic---an infection that occurs within the entire body.