How can I repair this?

I think the wedding has been and gone. The thread is over a year old

Oh dear. That looks like very floaty,thin material. Is that the underskirt?

You will have to be very careful indeed if you use any iron on stuff.

Get it repaired professionally. As it is near your feet you may catch it accidentally and make the hole larger.

To fix the snip, trim any loose threads with fabric scissors, then use fabric glue or make a small stitch to secure it. If you're unsure, a tailor can make a more professional repair.

Trixi try Etsy or any craft site they will sell wonderweb. Think eBay and Amazon will to. John Lewis sell lot of haberdashery things.

Thank you for all your replies. Lots of useful suggestions there. Going to have to search some wonderweb, although haberdashers are hard to find these days lol.

grannysyb

Tiny piece of wonderweb ironed on.

This

oh yes, dress side up and interfacing under as you need to see the edges

small piece of very lightweight black interfacing on the back. Cloth under and cloth over the dress, then keep the iron still to melt the glue on interfacing. Before putting interfacing on, just neatly trim off the torn thread that would stick out

If you want to wash and wear that dress again, then a couple of rows of small stiches to make sure interfacing stays in place

I used exactly that same method to mend a bigger tear in a dress, only yesterday

grannysyb

Tiny piece of wonderweb ironed on.

Yes agree.. . Or black small bit of iron on interfacing. Works a treat.

Just what I was going to put grannysyb.

A few tiny scattered rosebuds here and there along the underskirt.....?

A little clear nail varnish to seal the edges might work, but I think there is a dressmaker’s product for that purpose, used by costume conservators. I can’t remember the name though.

Tiny piece of wonderweb ironed on.

I would use fabric glue rather than try to sew it, but I am no expert hopefully someone more experienced can offer some advice.

Trixi
I don’t know how handy you are with a needle but this is where YouTube is your friend. Every conceivable repair is on there.