Black spot in roof of the mouth

A black spot keeps recurring in the roof of my mouth. This is the second time it's happened so I'm starting to get worried. It seems to appear out of nowhere, noticing it with my tongue.
The last time I was touching it and within a few minutes it had grown to three times it's size. So I looked in the mirror, getting worried at the size of it, I touched it slightly rougher and it just burst and blood came out of it. It was like bursting a blister, but then with blood.What remained then was a sizeable ulser.
This time I caught it early and burst it straight away, less blood and no ulser this time.

I saw somewhere that this might indicate mouth cancer, but I eat healthily, don't smoke, don't drink.

I do use Lysterine though.

I've been searching the internet looking for answers but I haven't seen this exact question(with the bursting and the bleeding) so I hope you can answer what might be causing this

[dove09]

Stop using Listerine, alcohol-based mouthwashes and even drinking alcohol has been linked to oral cancer. I am not saying you have oral cancer, but you should get the spot checked out by a doctor/dentist. In the meantime, you should gargle with warm (not hot) salt water instead of Listerine, and avoid fluoride-based toothpaste. I recommend this brand called Jason toothpaste with Coq10, "oral comfort" you can find it on Amazon.
http://www.upi.com/Science_News/2009/01/12/Alcohol-in-mouthwash-may-raise-cancer-risk/UPI-58671231779347/
http://www.amazon.com/Natural-Cosmetics-Non-Fluoride-Toothpaste-VeryBerryMint/dp/B000FGC9F8/ref=sr_1_1?ie=UTF8&s=grocery&qid=1252735820&sr=8-1