I've maxed out my character's attributes, but still have a few levels' worth of major skill points to earn. When I try to level up, I get a message saying perfection cannot be improved upon, no level up dialog and the level up icon remains in the HUD. Can I still level up somehow?
If your attributes are all at maximum, the game won't allow you to level up any further, giving you the message you received.
Temporary solution is to use a mod to increase the attribute caps: