Iodine and Methiolade
Read the general stain removal guidelines. Treat immediately. The longer it sets the harder it is to remove this stain. Use hydrogen peroxide. Protect the working surface with plastic to prevent stains to the surface. Pour on the peroxide, wait 30 minutes and rinse in cool water. Repeat if that improved the stain. If it did not lighten then it's permanent. Iodine is very difficult to remove.