If it was one of my dogs I'd stick him in the mag box, but you probably won't have one.
Go to Holland & Barrett and get some arnica tablets, and put some in his food, it'll tell you how many on the tub, this helps bring out any bruising, also witch Hazel is good for bruising, but not on a open wound.   
Good luck anyway, hope you get him sorted. 
  
http://www.hollandandbarrett.com/pages/product_detail.asp?pid=588