Hi,
I had a Mexican Black King that would get those whenever her cage was too wet. She had a horrible habit of tipping over her water dish and I never noticed on time. She got them twice, and both times I just dried out the cage completely and turned up the heat to absorb any more humidity, put Bactroban on the wound, and it scabbed over after about a week and then came off with the next shed. Both times it started out as a bump under a scale and became what yours looks like now. Bactroban is about the same as Neosporin but I believe the difference is it has a broader spectrum of bacteria that it kills and it's a bit stronger. Behind the counter stuff at the pharmacy and great to have around.
Hope this helps,
Kris