Warning light for headlights - but everything works?

Hi, just changed my ballast as my xenon wasn't working and that fixed the problem. I also changed both parking lights.



Everything was good but a day later a warning light came on for one of my headlights, then turned off a few minutes later.

Today both were on and never went away; checked and everything works (xenons, parkers, indicators and highbeams)



And ideas?