How long do you have a mark from a stingray sting?

That all depends on where you were stung and how bad the sting was.

For example: You got stung on your foot soul for about 2 seconds, and the stinger only went in 6mm. Because the soul of your foot is very hard skin, and the stinger didn't do much noticeable damage, it should only last for about 2 -3 days.