My Son Fell About 3 Feet From The Sink And

My son fell about 3 feet from the sink and hit his forehead on the flat top side of the tub (rectangular type of tub), he immediately got a knot on his head, and there's a simple like dent in the center of it that's really dark like blood. Took him to the hospital immediately, they took not x-rays or scans, just waited to see if he would hold down popsicles and water checking to see if he had a concussion. It's been 5 days and the simple like dent is still there and different colors. Could his head be cracked in any way is my question and am highly worried. I've asked him twice a day if he's had headaches and dizziness, and he has said no. He seems like his normal self, but I'm worried about the dent in the middle of the knot. He is 6 years old.