I would recommend to have your boy seen by a vet for the beginning of a fungal issue. it doesn't necessarily need to be ringworm, so a lab test (which only tests for ringworm) will not show up.
Could you please add your country to your details. We have members from all over the world, and medical brands, access to vets, climate etc. differs quite a lot. It would help us a lot to tailor any advice for what is really available to you if you please clicked on your username on the top bar, then go to personal details and scroll down to location.
We have got a UK piggy savvy vets locator on the top bar, but can provide a link with recommended vets in other countries.