Puppy traumatized after playdate

Hello,

I have a 4.5month goldendoodle puppy who has been an angel since we got him. Since day 1of bringing him home, he has been sleeping through the night and becoming really good with potty and obedience training. He is not easily scared or intimidated by new experiences and is pretty resilient. Four days ago, my husband made friends with this couple who have two 8-month-old Aussies, and he invited them over to our place for a playdate with our puppy. We've been taking our puppy to socials for weeks now and he has been doing well around other puppies so we thought we might give this a try. He is not the kind who directly engages with other dogs but runs around and observes with some playful barking occasionally, nothing that ever scares him.

The moment we met the two puppies outside our apartment, they got extremely excited and barking at him that it overwhelmed our puppy a little. We still decided to go ahead and brought them home because our puppy is usually a little shy initially in situations but warms up when given time. It seemed to have been going well initially, with all of them just sniffing each other and introducing themselves, and we did not realise when it got to a point when the three of them were just constantly barking at each other and cornering each other for almost 45 minutes. It was like our puppy started mirroring the exact behavior of the two puppies as soon as he was in his safe space at home. It was also our mistake not to have stopped the play, assuming they were having fun but after having read online, we now know that the play was very rough and our puppy was acting out in attempts to not feel as threatened. He never pees indoors and gives us signals to take him out (he's not going on walks yet because of vaccinations) but during the playdate, he both peed and pooped inside the house. The bigger issue started the next morning though. Our puppy has since then become extremely scared of everything in the house (assuming because the two puppies were in his safe space and he felt threatened) and is refusing to go to his potty spot, holding his pee/poop because he does not want to go outside to his usual spot that he's used since day 1 successfully, only strictly wanting to go indoors. He had gotten so good with potty training that he would roam around the house freely when up and now we cannot give him any free rein because he has just been going inside as soon as he gets the chance. He also never pooped anywhere other than his outdoor tray and would generally hold it until he can go in his spot but because he had held his potty for almost half a day yesterday, he pooped in the car for the first time when we took him out to socialise. He's eating, drinking and sleeping fine but just seems scared of everything in the house now and absolutely would not go potty outside no matter how much we reward him. he is still going potty twice a day but only because he simply cannot hold it anymore. He generally pees 8-9 times a day and yesterday he only peed thrice and it has me worried that he's gonna make himself sick!

I am very stressed that this one experience has ruined all his progress and he doesnt feel safe in the house and is not having fun at all. We love him so much and it's so difficult to see him struggling. My husband and I have tried everything possible that we read online to make him feel safe again and limit his freedom to his pen but he still seems to be scared after four full days. Any recommendations on how to make him feel better and if this is a bigger issue for us to seek professional help? Do puppies usually bounce back after stressful playdates? When can we safely start taking him to his puppy socials again?

We're hoping once he starts going on walks next week it might get better but for right now it's scary to see him holding his pee/poop for so long. I'd appreciate any help! thanks!