FIRST, before you do anything, save a copy of the photo & work on the copy. You can always go back to the original & save a new copy if you mess it up.

The best one to use is the "spot healing" tool, it's usually fourth down on the left hand side on the panel, looks kinda like a band aid. Have it fairly small & just slowly click over the offending marks. Normally you can just make the pointer completely over the mark, like in the case of a pimple, but it's a bit harder because of the shadows & creases around the nose, so you need to go slowly.