
There was a discussion on this on a Facebook group recently. Tails are notoriously difficult to heal for exactly the reason you state- getting knocked!
You could buy some of that foam tubing that insulates pipe and vet wrap it on, or a toilet roll tube, and I also shortly after found these which I didn't know existed:
http://www.bonovate.com/dogends.htmlPossibly salt water soaks would help to keep it clean but probably other people who have experienced it will have a better idea on that.
Jess