My DS split his forehead open, about an inch long and lots of blood. We took him to the after hours GP (it was located on the same grounds of the hospital, but for minor issues) and were seen within 30 mins. They glued it together, to prevent an obvious scar from appearing.
He has also split the back of his head open...LOTS of blood, and about 1.5 inches long. I chose not to have it stitched or glued due to its location, but i'm happy we had his forehead glued.
He's just go, go, go, so lots of knocks and bruises!