We went through this with our dog several yrs ago. The lump formed overnight,- on the bridge of her nose- we thought she had gotten stung by a bee or something. After a week we took her to the vet's and after some checking it was cancer. We operated then and there and when she came out of it all she ever sported was a scar on her nose with no hair growing. She lived another 8 yrs. so try not to worry.