+1 with bianchigirl and the other guys, no way to do that with your cycling shoes unless you use like a 10kg steel heel and toes shoes and I dont thing you use that at all.

Maybe the bike was like that and you did not notice or maybe somebody in you home handle the bike w/o you knowing it and the thing got a dent, but to get a dent like that in aluminum the hit has to be considerable. And due to the position that thing doesnt happens out of the blue, weird... always good to ask in your house you know.

The paint looks cracked but who knows if the tube has damage ok? the only way to know is peeling the paint and looking at the metal. If no crack in the material you are safe. That dent can be filled up and repainted.

Good luck.