Unless you scraped the bottom of the CPU is is unlikely that you've damaged anything. That being said, even the oils from your fingers can leave a residue that can affect electrical conduction and thus the performance or functionality of the CPU.
Were your hands relatively dirty or clean? Does the bottom of the CPU still look clean and shiny or is it heavily smudged or have other residue left over? If the CPU still looks basically clean, I'd advise doing nothing - the CPU is probably fine and attempting to clean it is likely to cause more harm than good.
If you see heavy fingerprints, smudges, or other residue I'd recommend GENTLY wiping the bottom of the CPU using a soft, clean, lint and static free cloth and some Isopropyl...