welcome. just give buddy some time to trust you, maybe be weeks or months and then he will come around. in the meantime, read around the forum, make sure he is on good pellet & hay, filtered water & give lots of wood to help his teeth from over growing. make sure if there is any plastic in the cage he isnt chewing it and he gets "healthy" treats like the occasional rosehip, or shredded wheat square, or steel cut oats, etc...
there are several very good people here that make cookies for chins and also sell food and/or wood.
Since I found this forum I rarely go to the petstore. Good luck. I love buddy's coloring.