Well, you can take Tylenol, like Vrickyi said. You might call your doctor or pediatrician and ask if Mucinex is all right to take. It really could break up some of that congestion.
I used to get incredibly bad sinus headaches that normal medicine couldn't seem to touch. What did help was plugging the bathtub and sitting down in the tub, with the shower on above me. I would put the water as hot as I could stand it, and then turn it even higher. I'd let the water run down my face and back, and use my fingers to pinch the bridge of my nose and kind of stroke/massage starting just above the bridge and pulling my fingers down my nose and then out across my cheek bones. I'd sit in the tub massaging my face until the water started to run cold. I'd turn off the shower and rest in the luke warm water in the tub. It really helped.
Carefully take a pan with a small amount of boiling water and lean over to breathe the steam. Placing a towel over your head to create a steam tent helps penetrate the congestion. It will take several minutes u must b careful not to touch the pan and get burned. Probably will need more than one pan of water as it cools off. Once u get the mucus moving out u can also clean out with a tepe pot or saline spray. You want to shrink the nasal membrane which saline helps do. Then put ice into a towel to make a facial compress. Also can apply ice to back of head / neck,
Sinus headaches are associated with a deep and constant pain in the cheekbones, forehead, or bridge of the nose. The pain usually intensifies with sudden head movement or straining. The pain is usually accompanied by other sinus symptoms, such as nasal discharge, feeling of fullness in the ears, fever, and facial swelling.