On my for arm theres a raised red spot that has a dark head and hurts really bad its red swollen has a head hurts and is really hard

See skin MD: I can't tell you exactly what you have. How long has it been there, has it enlarged, has it bled, are all important bits of information. Depending on these factors it could be an insect or tick bite, some kind of foreign body injury, or a skin tumor (benign or malignant). You should see a dermatologist asap to find out. This may require a biopsy or total removal for pathology examination.