Well, if it is a blister like thing I doubt it is melanoma.
Mine appeard like an irregular shaped mole suddenly on my shoulder. It looked and acted like a regular mole except for its irregular shape for years, until it started to change color. It did this for maybe 2 years before I went to a doctor.
If you do the black salve be sure you get the right stuff. You will need lots of Tegraderms (other names, Opsite, its a clear water proof dressing that allows air to move through the membrane) This is why I say talk to djt as she has direct experience but you can also go to
www.cancersalves.com The site for Ingred Naiman who wrote the book Cancer Salves. And if you choose to use this salve I strongly recommend her book.
The proceedure must be done carefully and explicitily by the rules.
I contacted Ingrid. She can no longer sell the salve due to legal problems but she did provide a contact for me, which I went and lost.
The book also explains other healing salves that are sometimes used for cancer under certain circumstances that you may want to know about. Make sure you have all the materials you need before you start.
I do not know of any particular remedy for melanoma within the heel products.. You can certainly give it a try as I do not think it would make anything worse.
If it is some kind of herpes it should itch or burn, the blister eventually break to an open ulcer for a while then heal over.
My mother in law had an unusual cancer on her breast that felt like a water filled sack. Not really a blister. Deeper under the skin. It was surgically removed and she was fine after that, over 10 years of no return.
As far as how much time you have before starting treatment. Who can say. Sometimes melanoma ( or any cancer for that matter) goes VERY fast, other times not so fast. Some cancers are known for thier speed or slowness in development but I have seen it both ways with melanoma. The variables can not be predicted. Watch it. I would measure it in millimeters and keep a record. There is no certainty that it is melanoma. There are other cancers that have a similar look as you described or it could be something totally different. This is why I would have a good dermatologist look at it. Correct diagnosis is very important whenever you go to select a treatment. You need to know what you are dealing with. "know thine ememey"
You know, when it comes to serious disease it is always my position to have a second opinion. Wrong diagnosis is made every day. You can spend a lot of time and energy living in worry, chasing your tail around.