I have a set of gas logs, the knob will depress to be able to light the pilot, but it will not turn any further to set the temperature. It kind of stuck earlier when I was blowing heater out getting ready for winter, then released and I was able to turn freely. Now that the weather is cooler again we needed to knock the chill off and now the knob won't turn again. Is there anything I can do myself to fix it?