Before you can even get close enough, you would either get poisoned to death by the ash in the air, asphyxiate from the lack of oxygen near the lava (gets burned instantly so there's air, but not oxygen) or, if you manage to get close despite those two, your body will boil, where your skin will blister until it erupts, tearing apart, along with your blood boiling your insides. When all that causes you to fall down, the hot rocks around the lava will probably cook you or flash-fry you depending on how close you've managed to get to the lava...
Have fun trying to test what will happen irl, you have our support! /s