Can you go to the Chemist and get some Normal Saline drops, or some nasal spray? It's what we use for kiddos admitted to our hospital with respiratory issues. You should just be able to get it over the counter, and what it will do is loosen the boogers in the nose so that they can be expelled more easily.
Thanks for that Kylie,I will go out to the Chemist today and have a look.Sometimes it seems like he has trouble breathing and it is so worrying.

neverplan -- Good idea,I actually thought it best to keep him upright as us adults know ourselves we can breath easier when sat up when ahving a blocked nose,But the suggestion with proping a blanket or something under his mattress is a good idea.