Hi thanks for your question.
I can understand your concerns.
that is nose bleeding has following common causes;
Local trauma that is nose pricking,
super added bacterial infection.
Increase in blood pressure to very high degree.
Then there are many rare causes for which you have been already investigated and you have none.
Blood pressure of 120/90 mmHg degree is not of that high degree that will cause bleeding, and this increase from 90/70mmHg to 120/90 mmHg is due sympathetic reaction to bleed.
There are less chances of re bleed, but you have to be careful of nose pricking, rhinitis that is common cold
and trauma to your nose.
Hope this answers your question.