2002 Mitsubishi Diamante Clicking/tapping sound while engin

My engine has had a tapping noise that has gotten louder over the past few days. Today the oil light came on so I went to change the oil. The engine still made the noise, but the light went off after I drove for a few minutes. They said it was 1 quart low on oil. Tonight I was driving and noticed that the tapping has gotten considerably louder and now the oil light is back on. I checked the oil and the levels are full. I thought maybe it was the lifters but am not sure what sort of noise/warning signs that would have. I do not know what to look for or where to even begin to check. Any suggestions?
thanks