The character is 安 (safe; secure; content). By itself, it is innocent enough.
However, "安" is also the last character in the name of a notorious Hong Kong Triad gang "新義安"
In short, this tattoo reminds me of this particular crime syndicate, consider it is on a bicep-- a body part that represents power and strength...
If the owner of this tattoo is a Hong Kong Chinese, I would stay clear of him, just in case.