How long has it been there? It could be an allergic reaction to a product you're using, but there are many possible causes. https://www.aad.org/public/diseases/hair-and-scalp-problems/scalp-itch
If you don't find relief using some suggestions for changing products or rinsing thoroughly, or if it continues to grow, I'd definitely see a doctor.
It's been here off & on for maybe 1-2 years. But it only bothers me at certain. I cant brush hair hardly. Its itchy & very painful. 2 days ago I had blurred vision all day & kinda bad.
I have hypothyroidism. And digestive illness. For last 2 years I have been to doctors, have had procedures, suffer from headaches, but that was for years as long as I can remember.