Actually, the vast majority of sinus infections resolve with self-care. Rest is actually a major factor in recovery. I'd assume this is only the first day of the infection, so its severity can't actually be told yet. I've known this guy a bit longer than you have, and he can tend to be a bit dramatic at times(no offense intended, Starfall). It hasn't been long enough for his mom to feel like it's an actual issue, as many sinus infections are minor, but if/when it does, she'll take him, I'm sure of it.
