Try putting some skin lotion on the bridge of your nose and it will help you a little. But if you do that way, your sunglasses may slide down from your nose and then it will make you feel annoying. You can try other glasses to see whether only this sunglasses make you get that pink mark. If does, don't wear this sunglasses any more and change for another pair.
It could happen to everyone while wearing sunglasses for a long time especially in the hot weather. So I suggest you take your sunglasses off ofteh and gently
massage the red spot with your fingertips. If you put a little
moisturiser on it, then the red mark will go away more quickly.