I haven't dealt with this personally but the scales are likely lost for good and that will always be a scar and have a shed issue. He may have rubbed in transit or in an attempt to shed on something too hard/sharp.
I see a lot of Jacks with shed remaining between the horns I find it isn't as much stuck as just "floating" in a space that rarely gets contact. After a couple weeks I take a damp q-tip and remove it more for my sanity than their health. It looks like the shed on his head is there because of husbandry and poor availability of plants to move through. Give it a few weeks and then make an enemy of him by trying to q-tip it off. I have seen many layers build up over time. Let him settle for now and see if he doesn't deal with it as he moves around in a proper cage. There is always the risk of creating more scars if you do too much rubbing, be gentle.
I see a lot of Jacks with shed remaining between the horns I find it isn't as much stuck as just "floating" in a space that rarely gets contact. After a couple weeks I take a damp q-tip and remove it more for my sanity than their health. It looks like the shed on his head is there because of husbandry and poor availability of plants to move through. Give it a few weeks and then make an enemy of him by trying to q-tip it off. I have seen many layers build up over time. Let him settle for now and see if he doesn't deal with it as he moves around in a proper cage. There is always the risk of creating more scars if you do too much rubbing, be gentle.