It is a sinus infection that has hardened into a cyst. His sinus cavity filled up with pus and mucous and it could not drain, so it began to dry and harden. After a couple months I would imagine the only way you will get it out of there is to cut it out, this is quite common and not as scary as it may sound. A link was posted on the other thread showing how to do it.
 
	 
 
		 
			
		
		
		
	
	
			
		 
 
		 
 
		 
			
		
		
		
	
	
			
		 
			
		
		
		
	
	
			
		 
 
		 
			
		
		
		
	
	
			
		 
	 
 
		
 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		