Hello...welcome and thank you for using Jutanswer.
So ,the noise started a few days after the oil change ,right ?
Just to make sure ,is the oil at the right level ?
Does the oil light come ON, when turning the ignition key ON and then go off after the engine start ?
Does the knock go away if you rev the engine a bit ?
Do you hear the noise all the time ,with vehicle on drive or in reverse ?
Can you remove the serpentine belt and start the engine to see if noise goes away ?
Can you drain a bit of oil and see if it shows any metal or a gray/silver color ?
Sorry for all the questions but I need to know o give you the best answer.
Let me know.