Wait in the trees for a while to see what the boar does. Perhaps it will go away soon.
Dash down from the tree, trying to avoid the boar and try to make it up Dan's tree so you can heal him before he loses much more blood from his wound.
Climb down and attack the boar, yourself!
Devise some kind of plan with the other party members! (please comment on details)
Some other creative option? (please comment)