Get some replacement shrink wraps ASAP... seriously! Most decent stores should have some, and the better stores with help and do it or assist/show you how to do it.. (or check some videos on YouTube)
The distance between the negative (almost the whole shell) and the positive (the top pin) is very small, and anything that will cause them to make a contact and the battery will fry, either vent (the hot liquid chemicals spits out) or you'll have a runaway (boom and fire).
The way that
batteries are "protected" is a ring on the top that protect the 1 mm wide insulation and the wrap that holds it in place. If you get that wrap caught on anything and the ring is pushed / bent, you're going to have a bad time.
If you can't find proper wraps, then tape them for now, anything is better than nothing, but with tape, you may have trouble fitting them in anything correctly and the tape might even catch on stuff more and rip it even more.
You can order these wraps from lots of online stores, and until you get them, you might want to set these
batteries aside safely.
Safety is always first with these lithium batteries. Really, the power and reaction they have is something to seriously respect.
That guy at the store that say not to worry is a * (select any word that means low intelligence), and I'd never take any advice for him again if I was you.
I meant it, going from slightly damage like that to the wrap ripping off is really easy to happen, and at that location of the battery, is the worst spot, and if it happens while in contact with a device, it will fry the mod or charger, etc. too.
Here's a video in case: