As long as it is real silver, no matter whether it is oxidized or not, it has no side effects on the body. You can wipe it with toothpaste to see if it is white. If it is real silver, you can wear it as usual. It is best to clean the silver needles of earrings before wearing them. Don't wear oxidized black earrings for a long time, which is bad for your ears. Just find a jewelry store to wash it.