Aryan gritted his teeth, his blood shot eyes glaring straight at Erian. His severed arm wasn't too big of a deal since it would at most take a day to heal but his expression soon changed as he realized his cells near his severed arm weren't regenerating but dying instead.
There was a massive amount of toxic radiation that had poisoned his cells, repeatedly contaminating and killing every cell they come into contact with. If this continues, his injuries would worsen and there would be no hope of regenerating his arm! (1)
Erian was far too ruthless! The amount of radiation placed in his attack had surpassed the amount his body's cell resistance could handle, killing off his cells instead.
If he didn't use his nuclear energy to clear the radiation, there would truly be no hope to regenerate his arm.