Dang- heirloom tomato fell off the vine, want seed

Hiya, I had this huge "maroon" tomato growing - knocked it off the vine when I were bringing them inside (8 degrees tonight in chch) so wondering. is there any hope for using the seeds to regrow it in future seasons!

It's a pretty massive tomato, very streaky green at the moment. As far as being ripe goes it's just not ripe at all. different shades of hard green only. Any thoughts suggestions or advice appreciated.

HAD to be the biggest out of the 3 heirloom plants grrr. Ps it had 8 leaves across the top! you know how they have those star leaves on the actual top of the tomato. some have 5 some have 4, this one had 8. It's mate still on the vine had 6.

PPs. The flower that started this tomato was the biggest tomato flower I ever saw lol. Ridiculous even, big multi petalled thing, sort of didn't even look like a tomato flower at all except for the general shape and colour. Looked part dandelion flower!

I'm sure you can use the seed to grow for next season .what have you got to lose!

thanks I just don't think it's mature enough, but I will leave the tom upside down in a sunny window spot and try it anyway:)

Good chance it will ripen now it's begun to turn colour(the streaks, I mean).