Suggest Treatment For Small Hole In My Scalp

I just noticed after working in the yard all weekend when looking in the mirror, after a bath, that I have a small hole in my scalp. I'm 34 years old, female, 5'6" and 150lbs. Please help cause I'm sort of freaking out. I stuck a needle in the hole to see how deep it is and it was deeper than expected but now that I punctured through the skin in my scalp it's throbbing!!