Rubbing alcohol. Take an absorbent paper towel and place it on the outside of the shirt over the stain. Saturate the shirt with rubbing alcohol from the inside, making sure the paper towel is pressed firmly against the outside of the fabric. You should start to see the ink come off the shirt and move on to the paper towel. Keep repeating this process, using a fresh paper towel as needed.
This is the way to go. It's worked very well for me on ink stains, though I've never tried it on such a large stain.
Everyone in this thread is wrong.
Use Acetone, AKA nail polish remover, on a cotton bud, not the one that goes in your ear, and one the acetone hits the ink
it will spread the stain into a lighter colour, repeat until you have diluted the stain completly and then wash in cold water.
To say everyone is wrong is foolish.
Only if the acetone reacts with and dissolves the ink alone without damaging the fabric dyes will this have a chance. I don't see acetone discriminating between the two, do you? If this were a white shirt I may agree with the approach but such is not the case.
I have heard of a few different ways to DIY a ink stain out of clothing but my nephew tried this one the other day and it worked perfectly. Milk and Vinegar. Two parts whole milk and one part white vinegar. Soak your shirt in this overnight. Here comes the weird part: Hang it up to dry and then wash it as you normally would after. Let me know how it works out for you!