I'm going to copy this from somewhere else, because it'll just be quicker. Forgive the she's in place of the he's.
If you got your chin 2 months ago and it's 3 months old, then you got your chin WAY too early from whever you got it. A chin should not leave it's mom until minimum 6-8 weeks unless there is a compelling reason for it (mom died, losing too much weight, etc.). The poor thing didn't even get enough nursing time in, no wonder he's upset and confused.
You need to have patience, patience, and when you run out of that, get more patience. In the end, it almost always pays off. You need to think of chins as chinavision. Fun to watch, but the interaction comes on their terms, not yours. In some respects they are similar to those cats who only come to you when they want attention, then when they have had enough, they leave.
Okay, that said, here is how I would go about trying to bond with your chin. First, start sitting by the cage and reading to them. Read the newspaper or a magazine, or the TV guide. The important thing is to let him hear your voice and learn that you're not going to hurt her. Hhe may not have been handled very much (or at all). If he came from a pet store, they were most likely poked, prodded, and mishandled before they came to you. He have a lot to "unlearn."
Second, after you have him accustomed to your voice, open the cage door and let your hand dangle in there while you read. He will come up to it eventually, and possibly nibble on it. Try, really hard, not to jerk your hand away when he nibbles. He isn't trying to eat you or be mean, he is checking you out. When chins groom each other, they chew on each other like that. It's totally normal. If he bites too hard, then yes, definitely remove your hand and there are some things you can do to help them stop that, but for now, let him explore.
Third, once he is coming up to you, bribe him! Don't use junk treats (raisins, papaya, lettuce, carrots, and any other host of treats not safe for an adult chin either), instead buy some bite sized, nonsugared shredded wheat or old fashioned (not quick) oats. If you use the shreddie, break it in half. Lay it on your palm, let him take it. After a day or two, try again, laying it on the back of your hand. Slowly work your way up your arm until she climbs up onto your shoulder. You do not want to overdo the treat stuff, so only do this every couple of days. Use treats very sparingly on him, especially since he's under 6 months of age.
Finally, try not to chase her around the cage. It just causes her to be distressed. Also, when holding him, hold her properly by grasping him at the base of the tail, right up near the butt, and putting your hand under the tummy for support.
After he seem more comfortable with you, and after he has grown a bit so he isn't using up needed calories, set up a chin safe play area. Bathrooms work great because they are self-contained. Make sure the toilet lid and seat are down, that there are no chemical bottles laying around, and that the bathroom is clean. Then shut the door and let herrun. Sit on the floor and read a book, and within a very short time he will be running up your leg, on your arm, your chest, possibly your shoulder and even your head! You just have to let him do it at his pace, not yours. The more you clutch, grab, and try to contain him, the more he is going to fight to get away from you.
Chins are extremely independent little guys, but still make wonderful pets. You just need to understand their temperaments so you aren't disappointed or frustrated. If you get frustrated or angry at her, she is going to know it and it's just going to make it worse.
