It does sound like the eye has been scratched by something. This usually results in an eye infection. My recommendation is to make a tentative appointment with a vet for tomorrow or at least locate a vet that is good with chinchillas. If there aren't any then find a vet that is experienced with rabbits. If the eye begins to clear up and is opened by itself by tomorrow morning you are okay. If not you will need treatment that usually involves antibiotics and painkillers. Be very careful about food and water intake. If you think it has stopped eating or drinking see a vet ASAP and be prepared to syringe feed. Most exotic vets will carry the supplies you will want for this. Pain from eye infections can occasionally cause anorexia that can kill a chinchilla and cause serious digestive complications that are difficult to manage if not caught early.
Also be careful that it does not go off its food during antibiotic treatment if given oral antibiotics since those often cause digestive irritation. You can clean around the eye with a damp q-tip. Having the eye stuck closed can cause complications if it stays that way for several consecutive days. If you see any irregularities on the surface of the eye such as a noticeable scratch or ulcer you should see a vet.
That is my non-expert advice.