If your fuel light is flashing, it means your tank is getting low on fuel. If you have a manual transmission, it's best to stop and add more fuel before the engine starts to sputter. Otherwise, you risk damaging your engine by running it out of oil.
There are a few reasons why your fuel light might be coming on sooner than expected. One possibility is that your car is leaking fuel. Even a small leak can cause the sensor that detects how much fuel is in the tank to malfunction, causing the light to come on prematurely. Another possibility is that you have a faulty sensor. This isn't as common, but it can happen if the sensor gets damaged or wears out over time.
If you're not sure what's causing your fuel light to flash, it's best to play it safe and bring your car into a mechanic for a diagnosis. They'll be able to figure out whether there's a problem with your car or if there's something else going on.