Experts recommend that you just wait a week or two and start over again.
When you start again, make sure that the timing is right. There should not be anything disruptive or out of the ordinary going on at home. Your child needs to feel that the potty training is not forced or stressful and it will become a regular part of his daily schedule.
Next, make sure that your child feels good about his potty. You may want to decorate it and let him help. You can even put his name on it. Start off by having your toddler just sit on the potty for several minutes. But don’t expect anything to happen. Just let him get used to sitting there for a time. When it does finally happen, make sure to praise him. He will eventually get it and you will forget how challenging this time was.