Unfortunately, you will probably have to just let it wear off. Dyes are picked up by the dermal layers, and as you shed the outer layers of the skin, the discoloration will also be shed. But, it will probably take several days.
There are some things that will take dyes and paints off, but you probably do not want to use any of these solvents on that particular body part.
(Back in the days before blue jeans were pre-washed, it was not uncommon to end up with your thighs and private parts turned blue, if you got the jeans wet the first time you wore them. We just had to let it wear off. So, to prevent that, we usually washed the jeans several times before wearing them. We had to do our own pre-washing.)
The best thing to do is just let is wear off. Sorry.