Whats the large sore on my cats nose?

Been there 4wks got larger but scabbing slightly
   
Help?

See a vet now. Could just be feline acne (which can be treated), but it could be an injury or infection that never healed, or squamous cell carcinoma, basically skin cancer! Which would need to be caught soon.
   
Whatever it is, see a vet now before it gets worse.

Hi, I appreciate the reply...
   
I went to the vet but wasn't left feeling reassured... He wasnt sure as to what it was - said it could be herpes (its not as the symtoms dont add up) or poss Pox Virus...She caught a wood pigeon over 4 wks ago and it had pecked her nose... It started off as what looked like a scratch/cut, which i bathed in warm salt water and thought would heal, it then spread and appeared to be eating away at her nose! It looked v sore and pink (she kept licking it!) Apparantly garden birds and rodents can carry the pox virus so I'm thinking she's got it from the bird. The vet didnt think it was (!) but gave me a 10day dose of anti-biotics. It'll be a week tomorrow. She seems a little better (she was never off her food or not purring) as its scabbing up but she keeps licking them off! Fingers crossed it is nothing serious but I was so worried that I hoped some other cat owner may have experienced a similar thing with their pet.
   
I have added a photo of Boo and her poor nose! This could help...