Personally, I'd err on the side of caution and step in when things look to be getting out of hand. This may or may not escalate into a big problem down the road, you never know. It could be the the puppy is just testing his boundaries with your other dog, who will let him know when he's gone too far, and the puppy will respect those warnings. BUT, on the off chance that things won't go so smoothly, I'd not let the puppy pester the other dog to the point where he's grabbing him by the head and forcing him to the ground.
The fact that the puppy is coming back so hard in response might mean that he's feeling defensive, which could end up being a nasty fight at some point in the next few months if one of them decides not to back down. My dogs play very rough and it's really loud. To an outsider it might look like they're trying to kill each other, but I can tell that they're both having fun and it's pretty mutual. Once in a while there's a tone to their play that tells me somebody is getting mad, perhaps because the other was just a bit too rough, and that's when I tell them to knock it off.
I was much more pro-active about supervising their play when one was full grown and the other was a young puppy. I'd interrupt for some OB exercises for treats, like sit or down and watch me, etc., and then I'd release them back to play again. Keefer was actually pretty bad about trying to play with Halo the same way he did with Dena, who was his half sister. She was nearly a year older and under 10 pounds less than him, so they were very evenly matched. Halo was a tough little snot
but she was only 14 pounds when she came home at 10 weeks old, so I was on him a lot to get him to play more gently until she was older and bigger.