How to fix the microphone on headphones?

I am not sure which Headphone you are using, I would say if you want microphone feature in a headphone then you should consider some good quality stuff that can work for longer. I am using Sony headphones with mic since 4 years and its working well to me. So branded stuff always makes a difference

Hi. This is old - but I am answering as I had a similar issue, except for it being Apple Airpods, not Apple earpods (similar sounding, very different) - both mics weren't working - and solved it fairly easily - and so I would hope someone sees this and tries it first before resorting to opening up their Airpods and breaking them.

All I had to do, before going to an Apple Store to get them replaced free of charge (if warranty covers), was to reset them by holding the button on the back of the case with pods in the case for about 40 seconds or so. You have to re-pair them with your phone / whatever. Mine started working perfect again after that.

I wouldn't advise mucking about with toothpicks or putting anything at all into your AirPods (Earpods might be a different story) - the metal mesh is tiny so that lint doesn't get in there. Wood fibres would get stuck inside instead if a toothpick was attempted to jam into those tiny mesh holes - and opening up an apple AirPod will destroy them - they do not go back together and are not designed to be opened up - and of course you would void warranty.