If by 'done stuff' you mean (penetrative) sex when you were a virgin before, it might be just some residual bleeding. By penetrative sex, I mean, penis going into vagina. I don't think that just fingering could cause bleeding even if you were a virgin.
Did you two use condoms or are you on the pill? If not, how recently was your last period?
Hi, it could be blood. Also, do you have any other symptoms such as itching, burning, discharge, Pain? You could have bacterial vaginitis. This can be caused by a new sex partner, just due to the change or it can be an infection. But it is often caused by a change in the pH of the vagina due to bacteria that normally there and if you use a douche or something changes the normal bacteria and you get an overgrowth of the wrong bacteria or a yeast it can cause problems . It can be tested for . If it is not blood then you should see your doctor to have a few tests.