Crabs will not really go away on their own once they hatch and make refuge in your pubic area and you'll need to do treatment of the crabs or public lice for them to go away and if you do the treatment for the crabs they should go away within the same day or after a few treatments.
Crabs are essentially lice in the pubic area and will not go away on their own without treating the crabs.
You can either go to a doctor to kill the crabs or public lice or use an over the counter lice shampoo to wash the pubic are to kill the crabs.
You can also try using some Apple Cider Vinegar to get rid of the crabs and if none of those home treatments work then a doctor can prescribe some stronger treatments such as a prescription lotion that will kill the crabs or pubic lice easier.
Shaving the area would also help you get to the crabs easier and make treatment more effective as well.