I Have A Open Sore On My Chin That Is

I have a open sore on my chin that is taking forever to close. I saw a dermatologist and he told me to put vaseline on it and then a bandaid and leave it alone until the next day. Then shower and then repeat. I had had a scratch on my chin that I kept putting makeup on, medicine on (cortizone, neo-sporin, etc) and picking at for about 8 months before I saw a dermatologist. He said it did not worry him because I had been picking at it for so long and kept opening it up. Also because I kept self medicating. I saw him in January, then went back two months later and he said it was making progress and that it would take a very long time. It was looking like the skin was coming back (I had dug a pretty good hole in my chin) but then I went on vacation and went swimming every day in a pool. Now I am worried that I have gone backward. What do you suggest?