my son woke up in the middle of the night and had a spot on his stomach about his waistline that itched. He scratched it and his hand came away bloody. he thought he scratched a scab or pimple and when he went into the bathroom to check it out he was kinda pushing at it and said something like a worm like texture and shape came out. when he tried to pull it out he said it felt like it was resisting. now it is an open sore with black around the edges and is sore. what could this be