As everyone else has said- a vet visit is warranted. Chins can get URI's, which can go downhill fast and progress into pneumonia. It's not a good situation, and the sooner it is treated, the better.
If it is a URI (which is sounds to be), your chin will need antibiotics..probably either sulfa or baytril. It would be a good idea to ask your vet for Critical Care if you don't already have some. Chins can go anorexic when they are sick or going on medication and you will have to start handfeeding them to keep them from going into GI stasis, which in itself is a whole other problem.