Well, as far as temps go and as a rule of thumb, you shouldn't be concerned until you get over 85 Celsius degrees.
If your GPU has sensors on the VRMs, check those too; they have different thresholds depending on how and from who the GPUs are manufactured, but you can use the same 85 degrees limit to stay safe (unless you specifically know their threshold).
If you're paranoid (I am), give it a good clean with a can of compressed air and/or a non-static-producing brush and you should be fine.