Its been there since i was young, as long as im aware. I am now 18 and i just googled it.
I swam alot as a kid, i dont know if that helps.
Picture:
https://ibb.co/fGz6AK
If you have had it since you were young, it's likely nothing to worry about. What you want to look for is if the spot is changing, growing, itching, or painful- at that point you will want to have a doctor take a look.