so i had a problem with the speedometer and odometer the ABS light was also on, we replaced the ABS sensor, and the speedometer and odometer started to work again, but the ABS light is still on. i dont know what this might be, or if i shouldnt really worry bout it

 

The ABS light on means that the computer has detected a fault in the system and has disabled the RABS. You will still have fully functioning normal brakes.
Easy things to check are brake fluid level, that both rear brake lights are working properly and that the plug connections at the master cylinder are clean and tight.
Also helps everybody if you post what the truck is.