That's not got anything to do with melanoma. The key features to be alert to for that are changes to things like moles. We all have lots of stuff on us, but it's when they change that indicates it might be a problem. I'm not sure how you scratched off a freckle, maybe it was something else. The only way to know if you have melanoma is to see your doctor preferably before you go and scratch off the growth and if your doc is concerned a biopsy of it can be done to check for cancer. You don't say how old you are, but it usually takes a long time for the body to develop skin cancer. But again, if you ever have odd growths, the only way to tell for sure if you're that concerned is to see a doc while the growth is there so it can be biopsied, as far as I know.