Is tamiflu (oseltamivir) dangerous if my child had nose bleeds and swollen itchy tongue from it? could other symptoms occur even if he quit taking?

Maybe: the swollen itchy tongue is worrisome for allergic reaction. I would stop taking tamiflu and contact doctor. influenza is usually self limited and tamiflu makes you better by one day. so keep monitoring your child, ensure hydration, treat fever with Tylenol (acetaminophen). and if he develops other symptoms like shortness of breath, go to ER.