White skin on side of throat

Hi,

OK this is very hard to explain but directly behind the tonsils there's skin/flap that goes down into the throat (not the back wall of throat). On one side this skin is normal red color but on the other it's white. I can't see the full problem as it goes too far down into my throat but can this skin be stretched/torn easily?

Just really worried as it's sore to swallow and white on only one side.