If the stain is on only the white, Clorox makes a Bleach pen that works miracles.
I have had good Luck with Liquid "Tide Bleach Alternative" not the regular Tide detergent.
Pour some on the stain, use a soft brush & really work it in & let it sit about an hour or a bit longer. Then wash in COLD water, take it out & do Not put it in the dryer. Spread it out & let it air dry to see if you got all of it out. If not repeat until it is gone or so faint only you will see it.