Welcome to HCM.
Your child most probably has a skin infection
which seems to be self resolving .
However it may take a couple of weeks for complete resolution . Meanwhile if the scab oozes pus persistently or there is worsening of the swelling and redness
around the scab then it's best to consult your doctor & apply a prescription antibiotic like mupirocin
or fusidic acid
on it thrice daily .
If there is new symptom like fever or pain or swelling the an oral antibiotic might be needed.
Keep the wound clean , dry and open for better healing.
Wishing you good health.