If you've already trimmed your pubic hair and it's itching as a result of being trimmed then there's not too much you can do to stop the itching of your pubic area until the pubic hair grows back.
But you can use some Aloe Vera Gel and apply it to your pubic area which can help soothe your pubic area and help stop the itching.
Or apply some other type of lotion daily to your pubic area where you shaved the pubic hair and that too should stop the itching.
But when you shave your pubic hair next time you can prevent your pubic area from itching by soaking in a warm bath before shaving your pubic area.
The warm water will soften your skin and be sure to use a clean sharp enough razor and then after shaving your pubic area apply some Aloe Vera Gel right after you shave your pubic hair to avoid it itching.