This is merely an internal conflict; as always, he has no choice. The Magic Potion has been bestowed upon him, and whether he likes it or not, he must drink it. This is also the Nether God's Court's way of testing his loyalty. Once you've taken the Nether God's Blessing, it's impossible to betray the Nether God's Court. Although he doesn't know what's inside it, that's what's recorded in the scriptures.
This has always been the reason he hesitated to drink it, pondering whether to consult Miss Virgo or Mr. Cancer and come up with a solution, or if all else fails, to run away. After all, he's either running or preparing to run.
