I am not sure I agree in this particular instance as it is only a gauge and if all other indications are correct then continue.
I experienced a complete oil loss in a single engine turboprop a few years ago. The engine continued to sound and feel normal, and all indications, save one, were normal. The only instrument indicating the problem was the torque meter. According to the manufacturer, the engine is capable of running a half hour with no oil. The only problem is that while the engine runs fine, there's no power to the propeller, even at full rated RPM...and consequently no thrust. I ended up on a hillside.
The quick response here is likely that it's irrelevant...after all, it's a turbine, and we're all private pilots here, we don't talk turbines, yada, yada. The example is relevant, however, because it's an example of a situation in which a single instrument...the primary power instrument, was the only thing telling the story.
I've had a power loss in a twin commander while descending in which no change in yaw occurred. The only indication was the manifold pressure gauge. No feel, no sound difference...just a gauge indication.
Don't make the mistake of thinking you can disregard your required instruments in favor of your own eyes and ears. You may not know as much as you think you do, and that ignorance could cost you dearly.
Your aircraft isn't safe, nor legal without the required instrumentation. The airworthiness certificate becomes invalid so long as it's not in compliance. You don't have all the information necessary to safely operate your aircraft.
Get it fixed, then fly. Any other way is irresponsible.