Katie: Hi Down here in the antipodes, the ambient temperatures can vary dramatically. With all the cars that I have owned before the Mk7, the temperature gauges used to rise and fall depending on the outside temperature (it regularly gets over 100 degrees Fahrenheit here). But the needle on the temperature gauge on the mk7 just sits on 90 regardless of the outside temperature. Reason why I'm telling you this, is that whilst I would get your problem checked, a dud temp meter in all likelihood won't be an immediate problem. The mk7 has a number of other warning messages if things go pear-shaped with the coolant temp.
But, yes I would get this checked-out at the dealer at the first opportunity