2001 Mitsubishi Galant Tapping sound from the Engine after

I recently got timing belt, water pump and Balance belt changed in my 2001 Mitsubishi Galant 2.4 L ES at 125000 by a local mechanic. Then I noticed a tapping/ knocking sound after the repalcement of those items. I doubted that the timing belt was not properly installed. So I went back to the mechanic and talked to him. He said that the tapping/ knowcking sound ( tiktiktik.) Is the sound of the lifter and it goes off after few weeks. But it did not go. He said that go to Mitsubishi dealer and ask them why your car is making such sound. Then come to us and let us know the problem. I am a exchange visitor teacher and I don't know many people here. Would you please help me what should I do? Do you think that the tapping sound is comming from the lifter? Do you think that they have installed the timing belt properly?