You will see increased temps on your computer.
However, modern CPUs (unless you're running a 486 you should be running one) should have overheating failsafes. Permanent damage doesn't seem likely to me. You're more likely to get random rebooting of your comp when you're running CPU intensive programs.
My bet is you probably dislodged something cleaning out the heatsink, but I can't reach that conclusion without knowing exactly what you mean by "eventually I on the computer then it doesn't boot up."