Hi Jane, Was this sex on the dry side, if yes then thats were your problem comes from, sounds like you may just have a small tear inside, for this the simple way would be to take a nice warm water sea salt bath and let this get inside you, it will help clean and help heal you, if you can just do this twice a day till it eases, but just keep of sex for a couple of weeks, next time you have sex use some extra lubrication, sex oil.
Good Luck
Two things come to mind. Maybe not enough lubrication or a possible infection. Can you get in to see the gynecologist to find out what's going on? If it is an infection, like yeast or bacterial, it will need to be treated. If there was'nt enough lubrication you could have small tears and that can cause bleeding.