So, sounds super-likely this was about abrasion that happened from the manual sex. And all there is to do about that is take a break from vaginal sex of any kind until the spotting stops.
In the future, it’s best for nails to be short and smooth AND to use lube, even if you feel wet. Our own lubrication just isn’t as good for high-friction activity like this. Using a latex glove is also a way to get a smoother surface and protect your vagina from abrasions due to fingernails.
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