Maybe the bruises caused by weed just caused your red eyes. So I suggest you to wear a pair of sunglasses next when you are playing in the weed with your friend. Usually the redness will go away after a few minutes or a few hours later. You can apply some artificial tears to flush out weed remains or use cold water to wash your eyes. You also should be careful in playing with weed next time.
Dear friend, if you are allergic to the weed, you may need to avoid touching weed next time. If you just mean that you get some weed into your eyes, you may need to remove the weed first. I suggest you to wash your face and eyes with cold water and then take a shower. This will help you get rid of these allergens.
Don't worry. The red eyes caused by weed will not last more than 20 minutes if you stay away from the weed immediately and get rid of weed remains (if there were weed remains) in your eyes. You should remember that do not rub your red eyes at this time for giving your eyes a good rub will cause further problems to your irritated eyes. You can lie down and put a cold compress on your closed eyes for 10-20 minutes.
Do you have tea bags or cucumbers in the refrigerator? If you have, you can apply two chilled tea bags or cucumber slice on your closed eyes. It is said that the ingredients in tea bag and cucumbers can calm down an inflammation and help reduce redness in the eyes. You can have a try! Hope you will feel better soon!