What exactly you mean by blood blister? Was it a blister actually filled with blood or was it just a pustule or eruption on your labia as inside vagina you can not manipulate. i need to know clearly to advice properly.
Was the itching after this bursting done by you?
Any history of recent periods which might have caused such an eruption. Any recent sexual contact - unprotected? It can be a sebaceous cyst too where the discharge would be fatty bloody discharge when you try to burst it open. Pl answer so that we can arrive at a proper diagnosis.
That was not the right thing to do as you might get infected / tetany etc. Now the bleeding that came may be from the puncture that you did using the pin. Now the best thing for you to do is to use antiseptic lotion or Hydrogen peroxide to wash the area to prevent any infection. If there is discharge from inside the vagina you should be alarmed. Just take care to keep the area dry as much as possible. The bump may be due to the unprotected sex and due to any unhygienic conditions at that time. Drink cranberry juice to keep the pH normal. Once after weekend go to your doctor for a visual check as i don't want you to follow any suggestions that come from unexamined sources.
Possibilities are more during unprotected sex and that's the reason for the suggestion to get a smear test done to rule out such a thing. there are cases of chlamydia where people go without any much symptoms but get diagnosed at a late stage. so please get an evaluation done to get cleared.