When the air filter is restricted as you describe causes a greater restriction in the intake, which causes greater vacuum levels. I suspect the higher vacuum levels pull oil past the oil seals and caused some smoking. I'm hopeful for you the seals and rings/piston are okay and would drive it some with caution to see if it cleans up with a clean filter/oil and as mentioned, I would watch it for a while before diving into the engine. A simple test would be to do a compression check on the engine and would be worth doing...