As long as the paste did not dry out before you put the heatsink back on, you should be fine. And as long as the heatsink and fan are secure, your worries should be over. Most CPU coolers have four lock nuts on them. Some just have regular screws. And I have even seen some very annoying ones that have "pop-in" pins, usually cheap plastic at that. Again, as long as everything is secure now, you should be fine. It is not a good idea to remove the heatsink once you apply the thermal paste. This can allow for debris to get in the mix, and once it dries, it will no longer provide adequate transfer of heat from the CPU to the cooler if you have separated it. Again, if you did so while it was fresh, and still moist, you should have nothing to...