There is no reason to be terrified, particularly if the freckle/mole has just recently changed size/shape. You don't say what size the mole is, and that's important when considering whether it's potentially melanoma. If you are concerned, it's always best to have a dermatologist look at it.
The "ABCDE" system is very helpful in identifying potential skin cancers: https://www.cancer.org/latest-news/how-to-spot-skin-cancer.html