I adopted a cat recently and my nose allergy is back. what should i do?

See details: Take antihistamines, consider allergy shots or give away the cat.

Allergy medication : You could try taking a daily antihistamine such as Claritin, (loratadine) Allegra, or Zyrtec.

"allergen avoidance": If you can, try to keep your bedroom cat free. This will give your nose a break from cat dander. If you can't do that, at least don't let the cat sit directly on your bedding. Avoid petting your cat and then immediately touching your face. Frequently use saline nasal spray or irrigation to remove cat dander from your nasal linings.