If so, then the logical answer would be that the wall absorbs most of the shockwaves produced by the explosion and protects you from the high quantities of heat produced. However, there is always the danger that the wall crumbles and takes you down with it. So if the wall is strong enough, get behind it, otherwise, run for your life.
Your question is very broad. I assume we are talking about the pressure blast itself, not shrapnel or heat from the blast, ONLY the pressure wave.
Think of the blast as a three dimensional pressure wave, as you encounter the wave, you typically have high pressure, followed by low pressure, before things stabilize to ambient.
For the most part waves are waves, ideally you want to break up this wave. Many bunkers are designed with 90 degree internal corridors.
Realize there is only a 14.7psi differential between sea level and "outer space" not really all that much.
From a human physiology perspective, the body can take a fair amount of pressure variation given enough TIME, to adapt and adjust.
The blast scenario pressure changes so rapidly, not much adjustment is possible on a physiological level. Ears and Lungs are usually the most easily injured.
Sorry for the long windedness, The wall needs to affect the wave, angle of the wall, proximity to the wall, etc, all modify the pressure exposure. I would think angle and proximity to the wall, could actually make things worse.
More specifics are needed, but being by a wall in the open can help:
As pointed out the body is pretty resilient to high ambient pressure.
So the major things causing damage are things hitting you, or you hitting them. A large explosion that generates little shrapnel will probably cause the most damage by tossing you hard and fast. This won't cause that much damage until you hit something solid...however if you're already pressed against a wall you won't get 'thrown' just pushed into the wall.
You will end up with twice the pressure on you due to the shock wave reflecting off the wall.