what is the blister on my sons face?

Posted by chicitita09

single blister type lump on each side of mouth one is on the bottom of lip other is closer to the cheek. one had yellow pus other had a black head and pus. when head came off left a burrow in one the other is going away. but the one closer to the cheek has a burrow and looks like its trying to go away but spread at the same  time. I have not found anything that looks like this blister. what in the worl could this be?