Can I delete a credit on my IMDB page

They are removable if you go through to the entry for the particular film or TV episode and edit the cast section.

The tricky bit though is that just removing the credit often won't be accepted, as , usually, someone played that particular role, even if that person wasn't you. So what you'd want to do is change the credit, so it points at the right person (and it is a nice thing to do for them, and the database too). It might be obvious if there is another person with the same name so a quick check might reveal who it should be changed to, but if it is completely wrong (as can happen) you'd want to find out the right credit. This isn't usually as tricky as it sounds as you might be able to find what you are looking for online (all for research purposes, of course) or if you ask in the relevant forum on the main IMDB board someone should be able to supply a screen capture.