This case report examined the natural course of reaction after accidental intramuscular administration of high dose Bacille Calmette-Guιrin (BCG) vaccine into the anterolateral aspect of thigh of a pre-term infant as a part of routine vaccination instead of intra-dermal injection into the arm. There is no consensus on the best management of this complication, although in this case healing was prolonged but was spontaneous without anti-tubercular chemotherapy.