And that's the problem. When it's first applied, it gets spread out evenly, and sticks to the cpu and cooler base evenly. With no air bubbles or gaps. If you pull it off, it's done. It'll no longer stick evenly, there will be air bubbles and gaps and that'll make hot-spots on the cores. Continued or even partial use can permanently damage a cpu as portions of the chip can get extremely hot in a matter of seconds.
I'd strongly advise you don't use the pc until after you look up the correct way to clean off a cpu/cooler (91% (or better) isopropyl /rubbing alcohol and coffee filters or other lint free materials) and buy a decent paste and do the job right before you fry that cpu. Heat damages to a cpu are permanent. Kinda like bad sectors on a hdd are permanent. There's no fix.
Good paste is cheap. I personally use Noctua NT-H1, Thermal Grizzly Kryonaut or Gelid Extreme GC. Costs @ $8-$13 for a tube, good for 3-5 applications.