I don't think it's coming on to tell you that you need preventive maintenance. I expect that you can turn it off by disconnecting the battery for a minute or so, on most cars this will reset the light and it can't hurt anything.

As you say if there's a problem it will come back on. Sometimes something will "glitch", such as a O2 sensor and trap a code, then once the light is reset it won't come back on.

Good luck,