I was trying to remove my P trap to remove a contact lense I dropped in the sink, but the plastic nut closer to the wall isn't loosening at all. I've been turning counterclockwise with a pair of channellock wrenches, but that nut isn't moving at all. I successfully loosened the first nut, however. Is there anything else I can do to try to loosen it? Thanks!

heating it might help but it also might ruin the contact lens.

Try posting a picture.

When you say the nut closer to the wall which one is it. Depending on how it's all put together you may have three nuts. One is directly below the sink tail piece which you said you loosened. The other one, which is n the other side of the U bend, is the second nut. Then from there there is a tubing that runs straight into the wall with a third nut, or perhaps it's not a but there but a rubber coupling there, or may be the piping runs on an upside down U to go through the cabinet floor. Which nut are you trying to loosen? Are these metal nuts or plastic nuts?

If you have a nut at the wall, you can loosen that one, along with the first nut, and back out the entire P-trap without having to touch the second nut, then empty it all into a bucket to find you lens if it's still there.