At the part in the DLC main quest where you have to
But when I first went there, I let him go on in and I went to do some side quests, ended up going back to skyrim for a bit etc. Now I'm back and the large door that he opens is closed, I don't have the object to open it, he does.

Anyone have any ideas? I do have a save from way back, near that part of the quest, but I'd rather not lose all what I've done since.