Its pretty clear from your explanation that the internal wire inside the external cable must have cut. So if you can do it yourself, try to locate the exact point wher it cut, get a blade or something to cut it open. Locate the point, take off the bad side. Then apply the blade on the internal wires, smooth to make sure you can clearly see the copper, then join back (colour- colour). Get a cellotape to wrap each of them to make sure they dont bridge. Then finally cover everything together to have one single straight wire and there you go. But if you cannot do this, then you need to give it to a repairer. Goodluck.
Answers & Comments
Its pretty clear from your explanation that the internal wire inside the external cable must have cut. So if you can do it yourself, try to locate the exact point wher it cut, get a blade or something to cut it open. Locate the point, take off the bad side. Then apply the blade on the internal wires, smooth to make sure you can clearly see the copper, then join back (colour- colour). Get a cellotape to wrap each of them to make sure they dont bridge. Then finally cover everything together to have one single straight wire and there you go. But if you cannot do this, then you need to give it to a repairer. Goodluck.