That is very difficult. It sounds as if the Metacam helps so it could be pain that's making him chew at it. Check the dosage and how often with the vet. It might not be lasting 24 hours and I have heard of people giving a half dose twice a day (tricky as it's such a tiny amount but can be prepared in something). But check with the vet.
Thyme tea is an antiseptic and people have used that for bathing wounds and it helps with healing. You just make up some "tea" with thyme. Fresh is best but dried is ok as well - in boiled water, steep it, strain it and let it go cold. You can then keep it in the fridge in a bottle and use it to dab on the wounds.
Is he in a hospital cage? It can help when they're recovering from surgery. Rather than being in their main cage where there are lots of activities and things they can catch the wounds on, you just set up a smaller cosy cage with paper bedding and plenty of nesting material. Maybe a little cardboard house. Probably not a wheel but it depends. It'll also make it easier to get him out each time for wound bathing or to check on him and general handling.
I had this as a hospital cage - it's quite small but has a front opening door (although it opens up so you have to be careful it doesn't fall down when open. But with the tubes removed (it comes with blocker pieces if the tubes are removed).
https://www.amazon.co.uk/Savic-Spelo...0643548&sr=8-1
If the wound has got infected though he should be on antibiotics again really. They hate baytril as well as it tastes foul. I took a very good tip to put it in a tiny bit of beefy dog food - and the hamster loved the dog food and ate it up every day. Just a pee sized amount.
You don't need to do that with Metacam - they usually like the taste but I did used to give it with food as ours didn't like the syringe. For that I'd put it on a pee sized amount of baby food. The baby food lids are quite useful for these small amounts to go on, or a teaspoon.