Tyre problem

When I drove out of the car park this morning, I knew that there was something not right with the car. There was a droning noise and it seemed to be coming from the front. I check the car and nothing seemed to appear abnormal. Ignoring it, I drove to Esther's day care and dropped Angela off at work. When I went out later, I decided to drive it slowly and listen hard. True enough the noise was still there. Stopped at the car park and checked the tyres carefully. I could not pinpoint that it seemed to be coming from the left. Then I saw it. It was a screw that got wedged in between the grooves. Went back the tyre shop where it was bought and they patched it. Upon further checking, there was another nail in the same tyre. No wonder I noticed that the air seemed to be escaping. They patched it up and since there was still sufficient thread, I did a tyre rotation. They did not charge me at all since I bought (or rather Stanley bought it from them and he passed them to me when he upgraded his car last year) it from there. The noise has disappeared. The next thing though is to change the brake pads. That will set me back by about $150 but considering that I am getting better ones than from the agent which costs almost double the price, I might as well get it done outside.