If your puppy does have an accident in the house do not rub his nose in it. If you didn’t catch it there is nothing you can do about it except keep a closer eye on him next time. If your puppy has an accident in front of you don’t scream and yell at him. Just take him out so he can finish outside where he is supposed to go and reward for him going outside.
It is fairly straightforward to house train your puppy, just remember… watch your puppy, take him outside frequently, praise for the behaviors you want and always stay calm!