Help with a certain situation about my guinea pigs

This is my first post on reddit so I am really sorry if I don't have the right format or if I mention anything I am not supposed to.

So couple of weeks ago I adopted two brother guinea pigs Norman(3m) and Duke(3m), they were never separated and always got along with eachother. However, this morning I noticed that Norman was unusually quiet and he tried to stay away from Duke as much as possible. I didn't think much of it and did the usual cleaning and refilling of foods and such. After Duke was done eating, he would approach Norman from the back and they would rucn around in the cage. I thought this was just playful until I saw that Duke wasn't just pushing him, rather "mounting" him and Norman would ALWAYS run away and try to either hide behind my hand or somewhere being an object. I tried shooing Duke and even got mad and yelled at him because he wouldn't leave his brother alone. This did not stop him. He would try to juke me or rush at his brother whenever I had to move to clean the rest of the cage. As a last ditch effort, I devided the cage in half with whatever I can find and Duke seemed to calm down. Not even 5 minutes later, I hear lots of loud squeeling from the cage so I run, and to my surprise, Duke DUG A HOLE through the stuff and basically ended up trapping Norman in his piece of cake (his house) and attempting to do the thing I mentioned earlier. With my rage, I immediately freed Norman, replaced the wall of stuff with a wood panel, and made sure Duke wouldn't be able to get to Norman again. Norman was absolutely terrified. He was shaking and would not move for a solid 5 minutes. Ever since then, he hasn't spoken a word even though Duke has tried very hard to get a response.

I am really not sure what to do so I would be really greatful if someone could let me know.

Also, I never had a Guinea pig before, but I am VERY sure that Norman did not want to take any part in that and he was genuinely terrified.