Basically, the microphone, earplug, and speakers all go through your sound card.. If the mic jack was shorted or caused damage to the sound device, all of them could fail to work, exactly as you've seen.. The "fix" depends on the situation and your skill at hardware replacement on your type of computer..
Unfortunately, you've not given us enough clues about your computer to offer much more... Laptop or desktop? Integrated audio or a separate card? Operating system involved?
If it's a laptop, and the sound card is toast, then the motherboard may need to replaced because you don't just slap in a new card.. If it's a desktop, then you might have a shot.. A replacement sound card might work IF other items on the motherboard haven't been affected..
Hope this helps.