@Becky where do you put the tissue? Is it ok if he touches it?
I had the same issue a week ago and it was really tough but she wouldn’t sleep without the dummy and couldn’t sleep with it in her mouth. I had to contact nap her on me all night for the first night. I did all the usual Vicks, olbas oil etc and gave her calpol. Second night I put onion slices in her sock at night and honestly it helped her a lot. Only thing is her feet smelt really bad next day lol but I did it for a few days along with putting Vicks on her and using a humidifier with olbas oil near where she sleeps. I also raised her head by rolling a blanket under her cot.
Have you tried olbas oil? I dab some on some tissue and put it near him and it helps clear his nose pretty quickly!