I have tested positive with covid19, my nose are blocked what can use?

Nasal decongestants: If nasal congestion is your only symptom, count yourself lucky. I hope it stays that way. You can treat the congestion the same as any common cold: saline nasal spray, perhaps a decongestant spray, maybe an oral decongestant or antihistamine. Probably most important, protect those around you: self isolate; if that's not possible, stay distant, always wear a mask, and wash your hands very often.

Agree with Dr. H: If you develop breathing difficulty, go to the nearest hospital, immediately. Wish you good health!