Chinchilla being aggressive?

I have had my male chinchilla for about 3 years now, since he was about 12 weeks old.
I left for uni and have returned once before since September. My last visit went ok and he seemed alright with me but this time he is very aggressive.
When I try to talk to him in his cage, he goes mad and tries to bite me through the bars. Just now I sat down on my floor while he was out and made no attempt to touch him or go near him and he ran up to me and bit me. He even broke the skin which he has never done before.
I am really confused as to why he is acting like this, especially since my last visit went okay. Do chinchillas forget people? I know they can hold grudges but I haven't done anything to him!

Wow that's weird! I'm interested in what others have to say...
I'm new to chinchillas myself, so I don't have much input ):

I guess it could be because you've been away and he's just not used to you anymore. You'll have to take time to rebuild your trust & bond. I hope things turn around soon!!

It may not be that he's forgotten you, so much as he's confused why you keep coming and going. Since chins take so long to adjust to new people (months), it may take him several days or even weeks to readjust to you being around. Idk! You may just need to give him a little more space and let him initiate interactions. I know it's gotta be tough since you don't get to see him that often! Try reading to him or talking softly outside the cage and giving him treats through the bars until he calms down a bit more?

Who was watching him while you were gone? Did they give him as much attention as you used to? If not, that could explain it. He could just have become un-socialized. If so, you will need to start over with him. The advice given previously will be a big help.

Its possible he was treated aggressively or poorly during when you were away and its somewhat conditioned him to be aggressive also.

i agreed with someone might have treated ur chin badly, otherwise i dont see a chin became agresive by no reason