A steady TPMS light means at least one tire is significantly below its target pressure, usually 25% or more. Check all four with a gauge and inflate to the placard figure, then the light should clear after a short drive.
A light that flashes for around a minute at startup and then stays on is reporting a fault in the system itself, not low pressure. That is often a failed sensor battery - they typically last five to ten years - or a sensor that was damaged or not re-learned during a tire change.
Cold weather sets off a lot of TPMS warnings. Pressure drops roughly 1 psi for every 10 F fall in temperature, so a set that was fine in autumn can trip the light on the first cold morning.
Never ignore it. We check and reset TPMS as part of a TPMS service.