Small scratch under eye of 4 year old boy 2 months ago still lettel red and depressed , does this will leave scar and if not how long to fade complete?

Scarring possible: A small scratch is more likely to leave what we call " post inflammatory hyper pigmentation" meaning a little dark spot where the scratch was. Depending on skin tone to start with, this may take 6 months to a year to resolve. Sun will tend to darken the pigmentation so be sure and help him with a little suncreen to protect the area. The xinc oxide sticks work well for smaller kids.