I took nyquil for a chest cold and 10 mg of melatonin before thinking of a possible interaction. is it safe?

Nasal saline spray is often effective in reducing the symptoms of an upper respiratory infection. The interaction should be safe but please check with your Pharmacist. Drink fluids,rest, monitor temperature and breathing. Have a Flu and COVID-19 vaccination. Watch for signs of shortness of breath.

Take Nyquil along with melatonin may increase side effects such as dizziness, drowsiness, confusion, and difficulty concentrating. Those are not life threatening side effects but you need to avoid tasks require alertness such as driving or operating hazardous machinery.