I'm not sure if you still can. If you ask me, 2draw is a bit fluky (or I am not quite informed) up until which point you can still delete drawings. But generally, to the left of these comments there should be an edit/delete link. And then on the bottom of the next screen you'll have the option to delete. If it isn't there, then you could try to ask a moderator to delete it for you. Or if you really don't like it, draw something else over it.
drawn in 33 min
But drawing over it is a really good idea:D thanks a lot!
drawn in 46 min
i like this one better.