From what you said, I should say, it is not a very serious problem. Because mold grapefruit juice is simply one of the most natural products and it is totally not chemical or something, but with some of it in your eyes, you might get some hurt feelings, but do not rub your eyes under no circumstances. Just wash your eyes with some clean water and get some eye drops to help.
It always happens for some liquid stuff to splash into eyes, such as shampoo, oil, soup, juice and so on. What you should do is to calm down and flush your eyes by much clean water. And do not rub your eyes for even your eyes feel uncomfortable. Take a clean towel to rub your eyes instead of hand. Your eyes will be recovered after a minute.
Don't worry, it is not a big problem. You even needn't consult a doctor. I once has get some grapefruit juices into my eyes. Though my eyes feel a bit of discomfort at the beginning. But nothing happen to my eyes latter. My eyes recovered soon. If you really worry about it, you can wash your eyes with clean water. Believe me, it will recover itself. Good luck.
Yes, it is very bad for you to get grapefruit juice into your eyes which will hurt your eyes and make your eyes feel not that comfortable. You could wash the eyes fully with the clean water. Then you could use the clean cloth to dry it. Then you could do the warm compress to make your eyes feel comfortable. You should do things carefully next time in order not to let the juice in your eyes.