Yes, that is definitely an abscess of some type.

Dr.Frye is going to be your best bet. You can call him. He will want you to email a photo. He will prescribe medication that can be sent to you via mail.

Being the size of the abscess, I don't think only topical antibiotics will be enough to treat the infection. He will need systemic antibiotics.

It really is nice of you to take him/her.