It pulls a little more fluid up into your cells after it is actively taken up, it's not a blood volume situation to even shift things acutely. It's not something that is associated with eating a little extra creatine intentionally on top of the normal intake and normal production in your body.
Blood pressure varies widely because of all sorts of very ordinary and common things throughout a day and over days.
Blood pressure will read high if the cuff is too small.
It is almost never taken correctly at offices/clinics and there's a good chance you're doing it wrong at home and/or the machine is not calibrated.
Chill.