What can i do to get rid of a big pink spot on my lip?

Last summer i went swimming and after that week i got a pink spot on my lip (probablymy second layer of skin on my lip) with black marks that accompany it. Can anyone tell me what happened or any rememdies i can use to get rid of it.What can i do to get rid of a big pink spot on my lip?
Just put lipsitck on it and go back to school.

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