If I read this correctly, you are at a crossroads intending to cross the major road to go straight on. A vehicle is approaching the same junction from your right but is indicating to turn left, leaving your exit and crossing therefore clear and safe to carry on. If you combine other factors with a turning vehicle, such as loss of speed on their approach or an indication of intent, I think you are correct to proceed. The fact that the other vehicle did collide with your car in the way you describe means they took the turn too quickly or the driver was incompetent in the manoeuvre. It would not be seen as reasonable for you to have waited until the other vehicle completed the turn as you might still be waiting there now, to exit.You MUST inform your insurance company as offences seem apparent.
Make this incident a learning experience.