What Causes Redness And Swelling In Forehead After An Injury?

My 10 year old daughter hit her head on the metal leg of a gym apparatus two days ago. She had redness and some swelling to her forehead abover her eye just under the hair line. It did not form a lump and the redness has gone. There appears to be a dent there. Is this something I should get checked out. She is complaining she has a head ache across her forehead. She seems well and is good spirits.