My 11 month old baby is severely congested, and cannot breathe through his nose when laying down. He wakes in a panic, screaming and is hard to resettle. What position is safe for him to sleep in yet will stop a blocked nasal passage? Currently he will only sleep in my arms

Have you seen your GP or Health Nurse with your baby?
Did they give any recommendations for managing his nose congestion & breathing?

Red Nose has some information about babies with a cold.
Research has shown that babies with symptoms of a common cold are often given more bedding than they need due to care giver concerns that babies showing signs of a cold need to be kept very warm.
In fact, providing assistance to babies with a common cold to effectively regulate their temperature is very important.
This can be best achieved by placing them on the back to sleep with the head uncovered and removing some bedding or clothing. If baby is overly warm to touch, or showing signs of heat stress (irritability, looking unwell, floppy, drier skin, refusing to drink or having fewer wet nappies than usual) then see your doctor or health professional immediately.
https://rednose.org.au/article/bedding-amount-recommended-for-safe-sleep

If you are still concerned about your baby’s health please see your GP or Health Nurse.
What State are you in?
There are some Child Health Services in different States that have an ” Advice Line” you can access.