Damaged volume flex cable after screen replacement

I've done many screen replacements on the iPhone 4s but this time, when lifting up the battery (from behind - with a metal spudger) i've damaged the flex cable underneath the battery, going from the volume button to the mainboard. The damage is pretty simple and tiny, but has caused the volume buttons not to work. No problem with the other buttons. Has anyone experienced somehow a similar problem and if so, how am i supposed to "solder/glue/<repair>" the cable?

Thx