Potty training upset...

We've had a couple wee's on the potty after morning nappy change but we normally put a nappy back on after but this morning I thought we would keep him naked from the waist down and just encourage the potty regularly. He did his morning wee and then every 20 mins or so afterwards we would remind him that wee-wee and poopoos go on the potty. He'd say okay but either wouldn't go or just sit there for a second and then run away. It was over 2 hours since his wee so I offered him a snack if he sat down for a wee, he sat while having the snack but then got up without having done anything only to then go to the corner of the room and squat down where he tooted and he was pulling at himself and I said if he needs to do poo or wee he should do it on the potty like he did earlier but he started crying and got very upset and leaked a little which made him more upset so I told him it's okay and said he can have a nappy on if he wants. We put the nappy on and had a cuddle and I said he can just tell me if he wants to use the potty for now but I'm not sure how to go about it now. I don't want him to get upset again but I know he needs to learn eventually...