cyst that burst

Question
I have a 16 year old Australian Shepard.  A few days ago she presented with what looked to be a scrape or small cut on her hip that bled and had some discharge.  I have cleaned it each day with peroxide and put clean bandages on it and it has continued to have discharge, although almost no blood. Yesterday, it appeared as a whole a little smaller than a pencil eraser.  Several years ago she had a cyst that burst, and this is what it looks like to me.  I can see clearly in the whole and no remnants of the cyst are visable.  There is still clear discharge.  Should I simply continue to keep it clean with peroxide and bandages?  Or should I take her to be seen by the vet?  If you recommend continuing what I'm doing, what signs should I look for that she may need to go to the vet?
Thanks so much for you advice,
  Carrie  

Answer
Cysts are common.  If you are treating it, you are only treating one small area of something resembling a balloon under the skin. The entire cyst cavity should be removed to get it to stop secreting. A local anesthetic, like lidocaine can be injected to do the removal without much danger to an older dog.