A 6-year-old boy from Mumbai presents with a 3-day history of impetigo on his left leg with honey-crusted lesions and surrounding erythema. Gram stain of the pustular fluid shows gram-positive cocci in chains. Culture confirms group A Streptococcus (GAS). The child has no systemic toxicity, normal renal function, and no signs of cellulitis or lymphangitis. What is the most appropriate next step in management?