To this question there are three points? Can you, may you, and should you.
Can you? If you're physically able, yes. However, you may be more prone to swelling and potential thrombosis. If your foot is in a tight plaster, it could become excruciating if there is no room for the expansion to go.
May You? The airlines would typically not challenge your ability to travel for something such as a foot.
Should you: In following the May You aspect, there is the important aspect of safety. You will not be permitted to sit next to an emergency exit, for obvious reasons...but I do countlessly hear people complain because they can't understand why, when their leg is in a plaster and they want more legroom, they can't have the emergency exit.
The greatest issue is whether you-yourself are capable of evacuating that aircraft in ninety seconds in the event of an emergency. Can you get down the door chute, jump up and run away from a fire? And, would your being on an aisle seat prevent the person on the window seat from being able to safely evacuate if you�re immobile.
I wish you a pleasant journey
Fr Bill