How do I clean an 1886 Nickle I found buried while metal detecting? It IS Nickle & first minting of its kind.?

I found this in my yard, about 8 inches deep in a sandy type soil. I can see the 1886 date, stars around the coins edge, and part of a Roman numeral V on the reverse. The trouble is that it is VERY dirty and I do not want to harm anything on this coin.