I think it's fine to tell him no - but then again you are giving him a reaction when he's chewing that (I just edited my post to add this). And giving him ANY reaction may be encouraging him. I would try moving him away from the cord and redirecting his attention. When it comes to chewing on buttons or jewelry or wires that are within their reach though - there's no stopping them
Whenever our tiel is on me I know I can't wear earrings or my husband can't have cords on him (like laptops cords or video game controller cords) - Lulu is determined and she'll get to the cords if they are on or near us. She won't seek them out though if we are not near or using them. Remote control buttons are also a favorite
