Cat lip

My cat lip under the nose is a bit red

Oh dear!  There could be many reasons for this.  It could be inflammatory eg an insect or nettle sting, or connect to the nose eg rhinitis or infection, or to rubbing the nose against something abrasive.  This is quite a brief description, so a vet who can examine your cat may be able to tell you more.

Oh dear!  There could be many reasons for this.  It could be inflammatory eg an insect or nettle sting, or connect to the nose eg rhinitis or infection, or to rubbing the nose against something abrasive.  This is quite a brief description, so a vet who can examine your cat may be able to tell you more.

My cat is an indoor cat he likes his lip when someone is eating

Lick lipping is normal to some extent, eg in response to food stimulus but not to the extent that it makes it sore.  Possible reasons include skin disease, or a bi-product of certain viruses, often with secondary infection eg bacteria or yeast getting involved.  A vet would be a good idea, if only to treat any secondary infection and, if primary disease eg skin, virus or whatever seems to be an issue, to look into that.

Lick lipping is normal to some extent, eg in response to food stimulus but not to the extent that it makes it sore.  Possible reasons include skin disease, or a bi-product of certain viruses, often with secondary infection eg bacteria or yeast getting involved.  A vet would be a good idea, if only to treat any secondary infection and, if primary disease eg skin, virus or whatever seems to be an issue, to look into that.