Please advise what is the best way to bring down a swelling or bruise on childs forehead?

Apply ice.: Immediately after the injury, apply an ice pack to the area, on and off for 10 minutes at a time for a few hours. There will probably still be swelling and bruising, which will go away after a couple of days, but the ice will help somewhat. If it doesn't, you should have your child seen by a doctor. If there is vomiting or loss of consciousness, you should also see a doctor.