My 20m girl was coughing throughout the whole of last night. And in btw, I could hear wheezing sounds when she breathed. What could be the reasons for the wheezing sounds? She doesn't has blocked nose not runny nose.

Wheezing might be her lungs not nose block. Thats y PD always check and listen to their lungs to made sure that it is cleared. Otherwise, there might be complications. I applied baby vicks on my little one when they have cough or cold. I rubbed on his chest, back and soles (covered with socks). It will help them sleep better at night. Do consult a PD if her cough persists as she is still young.