Spot On Back Of Scalp After Hunting. Why Does It Itch And Burn?

I was checking my 6 year old son s hair for ticks after he went hunting with his dad. I did not find any ticks but one spot on the back of his scalp had fine purple veins. He has never complained about this area, but said it itched and burned when I was checking it. Otherwise, he is healthy and active with no complaints. Are the small purple veins normal on a six year old s scalp? He rides the bus so I don t know if it has been injured. There are no obvious bruises or lumps .