It might be that the tracking is now out of adjustment - but this would normally be due to a blow to the front suspension. You did stay with the car while the tyres were fitted, didn't you ? If not then there's every chance that the tracking (front wheel alignment) was put out of whck by a joy-riding tyre fitter ! The other alternative is that one of the tyres has been fitted the wrong way around - inside out, or backwards if you like. Tyres are marked with a small dot to show which wall goes to the inside rim and which to the outside, or some are marked with the direction of rotation. Not all tyre fitters pay attention to this, and guess what the symptom is ? ? ?