Yes. Besides pressure on the ears, sinus infections can cause them to swell so badly that there is pressure on the nerves of your teeth. I've had them so bad on occasion that it felt like my hair hurt. A heating pad on low can help with the pain for a little while (don't let him sleep with it - you'll have to supervise). One of those air activated heat patches held in place with a head band or a knit hat might keep the heat where you need it without a burn risk.
Thick snot needs thinning. Use a humidifier, give him steamy baths/showers, have him drink plenty of fluids, avoid dairy for awhile if you can (some say dairy can thicken mucus), your Dr should prescribe an expectorant, although Robitussin is not bad, I'm not sure about dosage for one so young so stick with what your Dr says. Have him blow his nose as often as you can (put Vaseline on his nose now, his skin will get raw from dripping and blowing). If he's too young to use a neti pot, use a bulb syringe to rinse his nose with a mild slightly warm saline (2 cups warm water, 1 tsp salt, 1 tsp baking soda). He'll hate it, but he'll breathe much easier once you are finished.
He may not have a fever yet, but the mucus is a breeding ground for bacteria and it's common for a fever to appear several days later.