should i remove the cpu cooler & put it back??
You will need to re-do the thermal paste if you do that. The stuff Intel uses is almost completely dry, which makes it impossible to reuse and (most) people here frown on paste recycling anyhow.
My experience with re-pasting Intel stock HSF is that it does not work, high temperatures come back within days/weeks. I would replace it with something like a Hyper 212+ or 212EVO if it fits with your board+case+RAM combo and not have to worry about the HSF loosening up anymore.