He waited until almost the last second before jumping up and back, using his improved strength as well as a jump spell to get far enough to avoid getting gored. The inertia of the spear would mean it would still hit, and likely immediately break, but it would still do some damage. He had two heavier spears brought for just this purpose, and would repeat as necessary until running out of spears, before finally finishing it with his rapier. Or at least, that was the plan, and should work against a 'mere' animal. He might have a couple new holes to explain later, but it would be in good faith.