Symptoms of self-injury may include:

Scars, often in patterns.
Fresh cuts, scratches, bruises, bite marks or other wounds.
Excessive rubbing of an area to create a burn.
Keeping sharp objects or other items used for self-injury on hand.
Wearing long sleeves or long pants to hide self-injury, even in hot weather.
Frequent reports of accidental injury.
Difficulties in relationships with others.
Behaviors and emotions that change quickly and are impulsive, intense and unexpected.
Talk of helplessness, hopelessness or worthlessness.