It sounds like you are asking a couple of different questions here, all of which you should discuss with a doctor
. First, low blood pressure definitely does not cause nosebleeds. Rarely, nosebleeds can be caused by high blood pressure, although they are more often caused by trauma or irritation of the lining of the nasal passages. Very rarely, low blood pressure could be the result of a nose bleed, if the amount of blood lost was very significant.
I assume that the vomiting of blood was of blood swallowed from the nose bleed. Swallowed blood does tend to cause nausea and vomiting because it is irritating to the stomach. However, this irritation is not prolonged, and it should go away once the blood is emptied out.
On the other hand, if the bleeding
in the stomach was from another source other than the nose bleed, such as an ulcer or an inflammation of the stomach lining, then this is a more serious problem that could take a while to heal up. Typically, these cases are treated with medications to lower acid levels in the stomach and protect the stomach lining and close followup with a doctor.
Finally, it goes without saying that you should let an emergency or primary care doctor
know right away, especially if the bleeding or vomiting starts up again.