There are quite a lot of different reasons why you might have raised blood pressure and a lot are only temporary. I failed an HSE medical a couple of years ago due to hypertension, but when examined by my own doctor, nothing unusual was found and I returned to the HSE doctor and was passed. I haven't had any problems since.
In any case, there are quite a few drugs which control hypertension and will not stop you from diving.
Good luck, and don't panic
