Greetings - is this a heat boil or nodular acne or furuncle.? The diagnosis cannot be made with the limited history you have provided. Kindly see a qualified dermatologist near you or send in photos and further queries on practo direct. You may need a topical antibiotic ointment - depending of what the diagnosis is. Also dandruff can cause recurrent pimples on the forehead -so you can use anti dandruff shampoos which have an antifungal component - this would also help.