Some Topical antibiotics like mupirocin ointment could work if its mild.if its severe he must take some oral antibiotics like Cephalexin,Erythromycin or any other specific antibiotics. But doctor consultation is required before taking any antibiotics as some might cause allergic reaction to child.
The most important is about the Hygienic measures you should take about your child to prevent getting it or further spread.Keeping the skin clean,cutting the child nails short to prevent further infection could help.Talk to your doctor about the other prevention measures.