Accident in Austria, opponent in Austria, Austrian law and Austrian courts.
For an accident in Austria, Article 4 Rome II generally points to Austrian law. If the opponent is also domiciled in Austria, the Austrian courts have jurisdiction. The FIS rules apply as the standard of care, together with sections 1293 et seq ABGB.
Next steps: secure evidence, have the question of fault assessed by a lawyer and observe the three-year limitation period under section 1489 ABGB.