[help] My dogs got neutered and I noticed one isn't healing

My dogs got neutered on Thursday. The vet I went to kept them overnight. I went in Friday to pick them up and they told me my GSD had pulled his stitches out but he was okay. I've been checking them both every day. Tonight I went to check on my GSD and noticed half his incision has opened and it looks like it could possibly be infected. I left a voicemail for my vet and also emailed them a picture. I know for a fact I'll need to take him into the vet, but what do you think they'll do?

Will they need to put him to sleep to restitch it? Will an antibiotic help with the infection?

I planned on flying him in three weeks because I'm moving. Will he be healed by then?

[edit: typo]