Thanos hadn't broken Luke's bones.
Just before he was kicked, Luke adjusted the position of his bones and used his tougher and more durable muscles to offset most of the damage from the attack.
Elementary Self-Healing and Light of Life healed his injuries even before he straightened up.
In gaming terms, Thanos's combo didn't deal as much damage as Luke's automatic HP regeneration every second.
It wasn't hard to suppress Luke, but it wasn't easy to instantly make him lose his combat ability.
Sensing his physical condition, Luke had a rough idea. "Hey, lunatic."
He taunted Thanos with another voice transmission and cocked his head. "We're not done yet."
He tore apart the wreckage of the flier that he was stuck in and sent the parts flying.
They rolled over the ground and crashed with astonishing momentum.
