Hi
I am afraid its impossible to diagnose what any lump is without a vet examining and testing the lump with a 'fine needle biopsy.'
Some skin lumps are benign and others are malignant and need immediate and complete removal. At least its small from your description and if it doesn't look red, isn't sore or looking nasty in anyway then that is good news. Still needs a vet check though for the diagnosis. Sorry I cant be more helpful.
Cathy Wickenden BVet Med MRCVS
Barton Lodge Veterinary Centre
1 Midland Road, Hemel Hempstead, Hertfordshire, HP2 5BH
Tel: 01442 216048 24 hours
[
www.bartonlodgevets.co.uk]