Pulling a processor out of the zif socket with the heatsink can ruin the processor.
You must get a magnifying glass and look at all the pins carefully.
Make sure they are all there, and none are bent. If you tried to reinstall it, with the heatsink still stuck to it, you have most likely bent pins for sure, and might have even ruined the processor.
When you remove a heatsink, you must twist it left and right firmly, but gently until the heatsink breaks it's bond with the processor, so you don't pull the processor out of the socket....bad, bad, bad if you pull the processor out with the heatsink as you have just did, especially if the zif socket is still locked! Some older processors with small heatsinks you actually could raise the lever while the heatsink was still on, and pull them out together. Newer processors, you cannot do this, the heatsink is too big and prevents you from lifting the lever to release the processor. If you dont' unlock the processor, you are very lucky if you don't damage, or even pull some pins out of it. You do that, it is toast.
The only thing you can do now is use a sharp knife, and be careful or you will cut your finger off, or stab yourself, and work it under the edge of the processor and pry it off the heatsink. Hopefully none of the pins are damaged. If they are bent, you can take a mechanical pencil and slip over them and staighten them. All of this is tedious work, you must be careful. Do not damage the processor. Work very slowly, very carefully, and gently until you break the bound.
You will need to clean the top of the processor, and the bottom of the heatsink, reapply new thermal paste.
Last but not least, there was absolutely no reason to remove the heasink to simply clean it. You could have removed the fan, which should have came off easily by taking out 3 or 4 screws on the top, and then a few blasts of compressed air from a can would have done the job nicely.