What's this red bump on my dog's skin that he won't stop licking?

From your pictures, a possible cause might be a lick granuloma. These start for some reason (sometimes a bug bite, a small scratch, or a small skin mass) and the dog licks at them and makes it worse. They lick at it and push surface bacteria deeper which makes it itch, so they lick. It becomes almost a habit like a human biting their fingernails. So- I would recommend a visit to the veterinarian. They can check to make sure that is what it is , make sure that the inciting cause is gone, and do some diagnostics to determine a treatment plan. Has there been any changes to Neo's environment? Sometimes stress can start a lick granuloma or prolong it. Your veterinarian will most likely start antibiotics and anti-inflammatories. They might also recommend increasing his activity in case boredom is a cause. If there is a small skin mass present- they will recommend diagnostics on that. Good luck! Sometimes these take time, so have patience. Thanks for reaching out to Petco Pet Education Center, formerly Petcoach!