If your TPMS light is on in a steady state, one or more of your tires is more than 25% below the recommended tire pressure. You should stop driving immediately, determine which tire is low, and change it. Driving a tire that is 25% below the recommended pressure can result in tire failure, loss of vehicle control, or even a vehicle roll over.
If your TPMS light is flashing, there is a problem with one of the sensors or with the TPM System. You’ll need professional service, but check your tire pressure manually to make sure your inflation is still good.