Please help me with a boring question about curtains.

[EllebellyBeeblebrox]

My living room curtains have some kind of backing on (for shade I guess). The sofa chair has been rubbing on them and rubbed some of the back off so you can see it from the inside (not explaining very well, please see pics).
Is there anything I can put on the back to fix this? They're not super expensive curtains but I like them and can't afford any more at the moment :(
Thankyou!

Boring bump

I’d just stick some duct tape over the gap.

That's what DH suggested too! Will try that if all else fails, Thankyou.

Surely no one sees it?

You could hang separate curtain linings from your curtains to stop it getting worse and stop light getting through?

Not sure what the lining is on your curtains, it looks latex-y in the photos to me, but does this link look like it might be any use?

homeguides.sfgate.com/there-replacement-latex-backing-drapes-102669.html

Grey duct tape to the inside of the curtain (the side you cant see)

Looks like it maybe the similar colour

Thankyou all for your suggestions, very grateful