He first tried channeling pure mana to the holy light, trying to see if there would be any changes to it. For some reason, there was none. He couldn't weaken nor boost the power of the holy light with mana, it was actually rejecting it, clashing against mana and damaging Lyle a bit.
'Hmm, it's not mana but another source of energy, similar to the demonic energy that demons use.' Lyle thought as he changed his tactic.
Thanks to the fact he had poured the healing potion on the wound, it was already starting to heal, allowing him to relax a bit and do what would previously be considered dangerous. Without his healing factor working thanks to the holy light, he had to rely on the healing potion to do the trick.