@ Aquanero: Just like I thought. The splashing I heard during the night explains it. He must have scared himself and injured him bouncing into some of the wood. This also explains the tearing of his skin.
In the Freshwater Diseases and Health Issues section they also said it was a trauma.
As you can see on the pictures his iris is injured, that isnt the case with popeye. Also he doesnt have a full white circle of tissue around his eye.
I did some water changes yesterday and ill do some again, every day this week, hopefully that will avoid an infenction.
Thanks for the info!