30 y/o son had sinus infection & sore throat 4 past week, on augmentin 500/125, sneezed 3 x today & blew out blood, stopped in a minute, dry or worry?

Dry nasal passages. expected with upper respiratory tract infection, needs to have saline washes 2-3 times a day, together with continuation of the antibiotic as prescribed, if getting worse or no improvement in a day or two, see the doctor sooner, best wishes.