I don't know what the thermal limit is on that cpu, but you might be within it's safe zone. If not, then the best thing to do is reapply thermal paste. Wipe the old stuff away and apply a small amount. Just enough to cover it and smooth it out with a credit card. If you add too little, the heatsink will have gaps and wont make good contact. If you add too much, the paste will act as an insulating barrier and will increase cpu heat.
If that doesn't work, then you'll have to replace your heatsink. It might not be good enough for your cpu.