MacBook Air 2015 MagSafe charger is too hot to touch
Those are definitely the “high voltage” pins, if you consider 18V DC “high voltage.”
I would recommend getting a new charger to minimize damage and/or down time.
There’s a small IC in that adapter that communicates with the Mac to identify it as having whatever wattage your charger is rated at. When components get hot, it’s because something failed and now too much current is flowing through something.
As bad as this sounds, your potential damage is limited.

charger may fail meaning you can no longer charge and you have to buy a new one. This is moot because you should be getting a new one anyway
may blow the DC-In board. The good news is these vintage Macs has a separate board that interfaced with the MagSafe before sending power to the logic board. If the charger happens to burn this board up, it’s a cheap and easy fix to replace it

Both of these are more inconvenient than expensive. To be completely thorough, I must say it could damage your logic board, but that’s highly, highly unlikely. But, either way, you need to get a new adapter
And as adapters go, get the one with the highest wattage as you can always use a charger with wattage greater than or equal to what the device requires but not the other way around. So, since that’s a MagSafe 2 adapter, get the 85W charger.  If you happen to add another MagSafe Mac to your “stable” this charger will work regardless of the power requirements.