Open sore on my dogs left shoulder

Question
Hi Charlotte, I don't know if you can help me or not.  When I got home from work today, I noticed my 9 year old chocolate lab licking her shoulder.  I'd stop her and as soon as I'd walk away she'd start again.  I took her into a room where the lights are bright and sat down next to her to look over the area where she was licking.  Oh my gosh...there is an large open sore that is raised above her left shoulder.  It's not really bleeding but you can tell its the first layer of skin.  She's in no pain and is walking fine.  It's about the size of a small hard boiled egg and just that shape.  It is raised so the "sore" is protruding out of her skin.  At her last year's check up the vet said she had a small cyst under the skin.  Is it possible that this came through?  I've been searching the internet for an answer when I found you.  We are on a very tight budget so I didn't want to rush her to the vet.  I'm sure if I have to, the vet would work with us on payment.  Have you ever heard or seen anything like what I've described?  Sincerely, Kelly P.

Answer
Hi Kelly,

There's no way for anybody to diagnose this, especially without seeing your dog.
It's possible that the cyst your dog was diagnosed with grew over the past year and ruptured.

Do you know what kind of cyst your dog had? Fast growing cysts or tumors can be a sign of maglignancy, and should be examined by your vet. Some types of cyst rupture on their own. You should keep the wound site clean. Use an antibiotic rinse, such as Betadine.

A vet exam will put your fears to rest.

Best of luck,
Patti