emspace,
The bruising around the great toe is normal. Bone is very vascular and bleeds a lot when injured. Bruising will follow gravity, so because he has had his foot down in a dependent position, the blood will flow in that direction.
There is a lot of edema and blood in the soft tissues around the ankle and foot right now. The area will appear very inflamed, red and warm, for quite awhile.
He should still keep the ankle up, above the heart, not just on the couch in front of him. Elevated means, he is on his back, with the foot way up on the back of the couch. It really is hard to elevate a foot above heart level. But, by doing so, the edema and blood in the soft tissues will be resorbed back into the body.
I know, I know, it's hard to keep the foot up that much. But, whenever possible, get it up!!
However, if the elevation doesn't take care of the irritation or it gets worse, contact the orthopedic surgeon. Pain under a cast has to be taken seriously. There are many horror stories of patients being blown off, and ending up with a hugh sore under the cast. So, if it doesn't get better, contact the surgeon.
Good luck.