Is Nyquil The Right Medicine For Cough And Sore Throat?

i have a 12 year old son who took mucinex about 2 hours ago. he is very congested and coughing which is making his throat hurt. my question is, is it safe to give him nyquil? the label says for 12 and up, but he only weights 73 lbs, so i'm not sure 1) if he weighs enough to safely take nyquil, and 2) if he can take it after taking mucinex a couple of hours ago.