I am no expert, but an important part of fingering, whether someone is doing it to you, or you are doing it to yourself, is you must be lubricated. Your vagina self lubricates itself, especially when you are aroused. If you have a hard time self lubricating yourself, you can always buy lubricants from any local stores. I recommend going to a a pharmacy such as walgreens or cvs, and purchasing a WATER based lubricant. If your boyfriend was fingering you roughly and you were not lubricated enough, chances are he may have scratched you or irritated your vagina. I recommend trying to resist the itch, it will only make it worse. Try putting aloe vera on your genitals, but make sure it does not go inside your vagina. Wash the aloe vera off after 5 minutes.