What is to say it is too much for the pup and not that it just looks bad? Are they very different in breed sizes? How old is your adult dog? I would think if there is no aggression then they would work it out. But if it is getting dangerous I'd remove the pup to the other side of a gate or crate. Can you distracted the older dog with some sit and treat training if s/he is getting too much?
No tellings off. Just calmly separate them whenever you think it's getting too much. Tbh I don't think it does any harm for tiny pups and adult dogs to spend lots of time apart. There's plenty of time to build a relationship when the puppy's a bit older. Right now it's all about damage limitation.