seal the deal

Hello. is it the sentence “John and I finally sealed the deal-we became a couple.” correct? as in, does the idiom “seal the deal” apply correctly here?
thanks.

We put the seal on us- we became a couple.

?

It’s about coming to an agreement, but is usually used in business:

“If you give me a 10% discount that will seal the deal.”

I’ve never seen it used about a nuptial agreement!