This was posted by Noondaywitch in another thread
The red light should not be visible with no headphones in the jack; that's optical fibre output, which should be cut off when you remove the headphone plug.
The leaf contact in the jack is stuck. Try inserting and removing a jack plug a few (dozen) times.
If that doesn't work, try freeing it with a non-metalic probe such as a toothpick (plastic, so you don't get wood splinters in there).