It gets very bright at times...

..very, very bright indeed.

I should mention that my in-game brightness and contrast are at default so I assume this is intentional and part of the game, or should I keep a fire extinguisher handy in case my graphics card is having a meltdown?

yeah ... some of the bloom is really over the top - if you have a good gfx card, you should easily be able to manage it, but if not, there should be some options for contrast etc that you could turn down a bit.
Nothing to worry about though.

i was like (when i entered the game for the first time)

MYYY EYEEEEEEEEEEES

then i disapeld the bloom and blur effects after that it was cool

sometimes cuz that i see nothing but it's rare^^

HDR also affects the brightness. It simulates for example walking from the dark inside then into the light outside. You get blinded for a moment, then your eye's adjust to the light level. If you've ever played Elder Scrolls Oblivion, the best example of how it affects your game is the first time you step outside after the tutorial.