My kids were both big stumblers while learning to walk, and it increased exponentially when they were tired. You've got to do what you think is best, but I wouldn't take him to the doctor if he's behaving normally, pupils are the same size, etc. In the meantime, cushion the more dangerous corners in the house (coffee table, etc) or remove items that seem most hazardous, e.g. a footstool that would be easy to trip over. This will pass soon. He'll get more confident on his feet and fall less.