Diagnosis
The LED interior light is supposed to turn off automatically when the door is latched. If it stays on, the door switch that detects the latch is stuck in the "on" position or has failed.
How to Fix It
Try firmly opening and closing the door a few times. Sometimes the switch actuator gets stuck. Listen for the click of the switch when the door latches. If you're handy, you can access the switch by removing the inner door panel and checking for a jammed mechanism or broken plastic actuator.
If That Didn't Work
The switch itself is likely faulty and needs to be replaced. It's a common microswitch part. You'll need to disconnect power, remove the door panel, and swap the old switch for a new one.
Heads Up
Having that light on 24/7 won't hurt the dishwasher's operation, but it will slightly increase your energy bill and the LED could eventually burn out prematurely. It's more of an annoyance than a critical failure.