There is an easy way to do this which is used in many games.
Add Flash behavior to the player. When biker is hurt, start flashing for 1-2 seconds.
Add another condition "Is not flashing" to the event. This way while the biker is flashing, it's invulnerable.
Or you can do this with Timer behavior. Set a variable IsInvulnerable=True, start timer. On Timer event, set IsInvulnerable=False.