You can feed skinless, boiled chicken for a short amount of time, but if you cook the meat then you are eliminating the Taurine from it, which is an amino acid that aids with organ functions that cats cannot produce on their own, they need it either from raw meats (chicken, turkey, lamb, duck etc) or they need it added via a supplement pouch to cooked food or in their regular food. Its ok to go without for a day or so, but I would not allow it to go any further. Please get your cat proper food asap.
Edit: Just a heads up, TUNA is one of the worst things you can feed your cat, short of the toxic list. I would rather see your cat eat the chicken meat (not skin) from a piece of fried chicken than any sort of tuna.