Heatsink issues

[Mr_Pathetic]

I have a P4 3.0ghz with stock heatsink and earlier this week I was blowing out some dust and must have tried to remove the heatsink and did not snap it back down tight. Fast Forward to this evening and my PC decides to up and shut off. So I open case and notice the heatsink is loose and I snap it down. However when turning on PC it starts to slowly heat back up. When I remove heatsink what is left of the thermal compound (I never added any, stock pad/compound) it is completely dry and no longer tacky like it once was. So is it safe to say that I need to go grab some Arctic silver 5 compound and clean it off and apply the Arctic compound to stop this or have I done some damage?