It might be an infection of the hairfollicle.
Try to apply antibacterial ointments like mupirocin
, thrice a day.
If painful, you may give Acetaminophen
syrup in a dose of 15 mg/kg/dose, repeated every 6 hrs.
You may also give warm compresses in that area.
If it increases in size/ persists for more than a week or if your child gets fever, do not hesitate to visit your Pediatrician
. In such cases he might need oral antibiotics
and drainage too!
Hope my answer helps you.