Tips to help congested baby

My son is 18 months and has been congested the last few days. He’s fine during the day, running around and acting like his normal self. But the last two nights he’s been up every 30-45 minutes from congestion. We’ve tried nasal spray and a humidifier but he’s so miserable 😣 I’m afraid to put anything under his sheets (to help keep his head up). But I’m not sure what I can do to help. Currently the only thing that works is me holding him but I’m not comfortable sleeping with him in a chair