With any atomizer/clearomizer/etc., if you let it get too dry or don't allow enough time between puffs for the atty to cool down, you run the risk of burning the juice on the wick. If you look on youtube you can find tutorials for how to rewick your atomizer. Watch any of these to see how to disassemble your piece.
Once you get it disassembled, look at the atomizer (coil of wire around wick). If it is burnt, you will be able to easily tell.
To fix it, dry out the wick as best as you can with paper towels. Be sure not to smash the coil of wirewrapped around the wick (the atomizer).
Once its as dry as you can get it, use pliers to hold the atomizer and wick in a hot flame, like the one on your stove or the one produced by a wind-proof butane lighter. (you want a blue flame)
Hopefully your wick is silica, and will just heat up and burn off all of the old ejuice. If its cotton, it will just burn... You probably want to try just the tip of the wick first so that it doesn't all go up if it is cotton.
Don't leave the wire in the flame for too long or it will become brittle. Just heat it up till it and the wick turn red and then pull it out and set it someplace to cool. It will be hot for a minute or two, so be careful not to burn yourself.
Note that the wick will pop and sizzle due to the ejuice that is already in it. You want to replace your wick after cleaning it this way more than once, especially if your wick gets torn at all.
Hopefully between my suggestion and all the other great ones here, you can get the taste you want out of your piece!
(note that with any new wick, it will take a while to break-in, and will taste funny. It shouldn't taste metallic or burnt, but just be aware that if you rewick you are gonna have about 50 puffs till it tastes normal)