Welcome to BYC....
They look like scabs from an injury.. I am not sure if you have had turkeys long enough to know this little fact.....BUT please do not take this wrong,,BUT
Turkeys are not the brightest creature God made.... They find amazing ways to hurt themselves. It could be a fight with a rooster or another tom...it could be crawling into a small space and raising his head 47 times into a nail..
I would not worry unless they become raised or pus filled. (or something other than just a scab. If you can hold him, look for fleas, lice and mites, I have never seen a bite on the head like that though..
Do you have flies or other biting insects around? However I would think those would be raised a tad more. What about a feeder he could scrap his head on while reaching for food.
Lets see what
@casportpony has to say, she is way better than me at this stuff..
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https://www.backyardchickens.com/threads/a-century-of-turkey-talk-2000-2100.966414/
We would love to have you, a bunch of good friends talking about our lives and turkeys..(they are the same)