how should I care for wound on cat?

[Joyce A]

My cat, an indoor/outdoor neutered male, got into a fight and was bitten by another cat. On Thursday night I discovered a large swollen place on his upper arm. I took him to the vet on Friday, and he was given a big anitibotic shot that is supposed to last 2 weeks. The vet discussed with me surgically opening the area and placing a drain, but then he decided that since my cat may not stay indoors for the healing process that I should just "watch" the wound for a day or so. Today, I noticed that the wound has opened and is draining on its own. My cat has licked a large area at the puncture mark and the fur is gone. When he comes indoors, I bathe the area with cotton balls soaked in warm water and gently press the site, removing more drainage material. He is taking Metacam, too. I didn't think to ask the vet if I should do anything more to the wound site, such as the application of antibotic cream, etc. I am trying to keep it open with the care I'm administering. Should I do anything more than what I'm already doing? By the way, please understand that this cat was a stray, a "street" cat when I adopted him 5 years ago. I wish I could make an indoor cat out of him, but he insists upon spending time outdoors. I'm always afraid I will be labeled a "bad cat Mama", when I truly love my cats and give them the best care I can. I'm just asking if there's anything more I should do. My cat is eating and purring and seems to feel well.