Can't agree with the others more a fine needle aspirate will tell you more, while not trying to frighten you it is better to be safe.
Our very fit and healthy male stafford just before his 4th birthday had a tiny lump on his back toe that the vet said at his age was probably nothing but after a week on anti histamines was removed just to be on the safe side turned out to be a grade 2 mast cell tumour.
Good luck
Eric and Linda