I looked back at the OP's recent threads.
I saw several threads about persistent fin rot and clamping for Lucky Blue. Some of those talk about using aquarium salt, oak leaves and Triple Sulfa.
I saw one thread about a white spot for a different fish. The white spot was on the fish's side (not head) though. http://www.bettafish.com/showthread.php?t=116885
But I didn't see a thread about a white growth on a fish's head.
I would still like for the OP to post a photo and fill out the info sheet, or refer us back to a previous thread about the fish. I think this would allow people to determine just what's going on with this fish, and determine if euthanasia is appropriate.