On the projectile itself, have a FSM. Use the action "Collision Event". Use the store collider variable. Filter the collision by tag (probably "player"). Then when it hits the player the store collider variable will populate with whatever it hit (anything with the player tag).
In the next state, use the action "Send Event". The target of that event should be "store collider variable". Make sure the event is global.
On your player, or any other things you want hit, setup that event. Following the event, you can setup whatever "method" (aka string of states), you want triggered.