Got nasal polyps after recovering from a flu is this normal ? should i take it serious?

Nasal polyps usually form after prolonged inflammation of the nasal mucosa - chronic allergies, chronic sinusitis. Uncommon to form after a relatively brief episode of viral URI

Polyps are more of a chronic problem. They will cause nasal obstruction and should be managed properly. Best to have allergy testing performed and you should see an ENT or allergy specialist for further treatment options. These are treatable.