What’s worked for your fearful dog?

I have a 2yo corgi/sheppard cross (rescued at 5 months) that had a bad experience in our park a few days ago. Someone fell off a bike nearby and it really scared him.

He’s always been shy around people, (never lunges or barks) usually shying away with his tail tucked. After the incident at the park I can barely walk him, he only wants to go home

So what’s worked for you?