This all really depends on your experience and competence.
If you’ve tried changing a light bulb and found it hasn’t quite done the trick, then it might be best to contact an electrician. It could also be a light switch issue, in which case you could be looking at fixing a light switch or replacing a light switch altogether.
If you’re in the process of redecorating or renovating your home and you suspect a fault, again, you’re best to speak to an electrician before attempting anything yourself.
However, if you’re a competent DIYer then replacing the light fitting for redecorating shouldn’t be too much of a problem.
If you have any doubt when it comes to electrics, then you should call in a professional.