im only gonna drive it for 20 miles or so
and its been on for like 4 days and i haven't been driving it a lot
will anything happen if i drive it tomorrow ?
whats the worst thing that could happen ?
its been on like a week, and sometimes i hear a screeching sound from the brakes..is that bad ?

If the light just came on very recently, you should be ok. Avoid situations where a sudden stop is required and get them looked at soon

yes you can but if they get to low they will ruin your disks

If it just came on, you should be OK, but DO NOT forget about it!!!