I know it can be really hard to tell but have you noticed if the injured foot is cooler or warmer than the other? Cold would indicate loss of circulation and hot/very warm would be infection. It could just be bruising. In a person you would want to reduce swelling with a cold compress to help prevent tissue damage and loss of blood flow. Asprin would help with inflammation too but I have no idea what dosage to use and it might cause more bleeding inside the foot if it is a bruise.
I hope it recovers.

I hope it recovers.