How can I fix a small slightly damp area in my basement wall?
Water IS getting to it. There IS water there. You cannot fix it by covering the wet. You must fix it by stopping the water from getting to that point.

Check your gutters. Do they tend to get clogged? Are the downspouts set so the water is directed away from that area?

Check the grading in that area.

If all of this checks out, then the water is getting through the wall. There may be a crack. You may need to dig down and apply water proofing in that area, or repair the crack.