Yes.. If you took the CPU fan off, you will need to apply new thermal compound. Also, you'll need to clean the old thermal compound off both your CPU and CPU Fan. Isoproply alcohol on a lint free rag is the best method to remove the thermal compound... IMO
I would purchase Arctic Silver 5 (AS5) for about $7. Apply a pie size dot in the middle of the CPU and apply the CPU fan back on. You should be good to go with that part of the cleaning process.