Mysterious lump on dogs paw

Hi, I have a 4 year old black Staffordshire bull terrier. In the past week I’ve noticed this pink hairless-ish lump appear on her paw. As far as I’m aware it doesn’t cause discomfort to her. It’s quite hard and getting bigger. I’m just concerned. Could someone tell me what this could be?? 

Hello!  From this angle, there are many possible explanations.  This could be an area of inflammation and hair loss eg linked to demodex, or over a protruding bone, or rubbing against a boot, or atypical ringworm or chronic lick damage or a lipoma or foreign body or a tumour.  I'm sure that there are many other explanations.  Please do show it to your vet for closer examination in case they would like to do tests.

(once they have examined the lesion themselves, in context of the patient).