The Microcyn is ok.
I would suggest that you give him a round of antibiotics. Do you have any on hand?
At minimum, I would go to TSC and get a bottle of Procaine Penicillin G. You will need a the smallest syringe you can find and a 20 gauge needle. He's small so I would dose him at .10ml per pound of weight injected into the breast muscle alternating sides once a day for 4-5 days.
If you can quickly get Amoxicillin (see if you can order those from your TSC - fish antibiotics) that would be better than giving injections.
Did you leave one end open so the wound can drain?
@Eggcessive may have some better suggestions for you too.