MrCat has a little lump on his face, just below and in front of his ear. Nothing visible, can only be felt. It is firm, moveable, about 7mm wide. He does not appear to be in the least bothered by it or by us touching it.
What might this be? Does it warrant a trip to the vet? MrCat gets extremely distressed in the basket and then the car, so I don't want to put him through that unnecessarily.