I need help with my baby brother being sick someone help.?

My 7 month old baby brother is sick he is congested he has a high fever and probably feels extremly sensetive. My mom gives him a few drops of Nyquil everytime he starts to cry i want to know if there is a way for me to cure his fever. and if giving him any dose of nyquil dangerous and how (so my mom can beleive me)