Ford focus, 2018, engine light on

While you can still drive it with the fault, there will be a few things that you will find out, the two main things being an increase in fuel consumption as well as the fact that you won't be able to pass an emissions test (if in a location that requires emissions testing, some places will report this to the DMV and can have the registration suspended)

If it has less then 80k miles on it it should be covered under emission warranty... but take it a gastation shop or something to make sure it’s not cracked or broken. Also those cap less fuel necks sometimes get dirt in them and leak... use the funnel that came with the car and finger it a few times and clear the code and see what happens