Use Dawn dish detergent and rub it into the stain and wash the shirt in the washing machine on a regular cycle. The stain should come out.
Did you iron it inside out? Usually with these silkscreen designs you should never put an iron directly on the ink itself. Gotta be very careful ironing items like that. Always inside out, and always a very cool iron.
I can't find any store that sells this particular t-shirt, but I have a recommendation for you. There are many websites that allow you to create various items, including t-shirts, with a logo you design yourself. You then have the option of selling t...