Congrats on digging the Indian. All that one needs is to soak in some hot soapy water for about 15 minutes and then take a very soft tooth brush and gently clean it. After it dries I look through a magnifying lens and clean the nooks and crannies using toothpicks.
Nice old Injun'.
I would probably use a little soap and warm water and maybe an olive or mineral oil soak for a few weeks.
You surely won't hurt it and may even bring out a little more detail.